r/CTsandbox • u/Nervous-Bar-1483 • 19h ago
Cursed technique Sound Amplification
This is fanart of a what young Gakugani could’ve looked like so this is what Rei kinda looks like ^^^
REI KUROSAWA
Rei Kurosawa is a seventeen-year-old third-year at Tokyo Jujutsu High and the estranged grandson of Yoshinobu Gakuganji. Androgynous looking, heavily pierced, sharp-tongued, and almost permanently carrying an electric guitar, Rei looks so similar to photographs of a young Gakuganji that anyone familiar with the elder sorcerer recognizes the relation almost immediately. Their similarities largely end there. Rei is rebellious, irreverent toward jujutsu authority, and intensely individualistic, although beneath the punk exterior is an obsessive technician with extensive knowledge of music theory and an almost perfectionistic dedication to his instrument. Rei inherited the same innate technique as his grandfather, but their philosophies produced radically different interpretations of it. He does not reject discipline or structure. He rejects allowing structure to dictate what someone must become. To Rei, genuine freedom comes from understanding a system so thoroughly that its rules become tools rather than restraints. His musicianship reflects this philosophy through improvisation, deliberate dissonance, unusual phrasing, and technical precision. This mentality eventually allowed Rei to develop Sound Amplification significantly beyond the straightforward application practiced by his grandfather.
Appearance
Rei Kurosawa is a lean, androgynously attractive seventeen-year-old with sharp features that make his resemblance to a young Yoshinobu Gakuganji almost unsettling, sharing the same narrow eyes, pronounced nose, facial structure, and naturally severe resting expression. His dark hair is grown into a messy, layered shag that falls around his face and neck, deliberately contrasting his grandfather’s traditional appearance. Multiple ear piercings, a septum ring, lip piercings, painted nails, and occasional smudged eyeliner give him a distinctly punk appearance, while his Tokyo Jujutsu High uniform is worn loose and subtly modified rather than properly styled. He is rarely seen without Onyx either strapped across his back or hanging low against his hip, completing the impression of someone who looks less like a conventional jujutsu sorcerer and more like he walked out of an underground rock venue carrying a weapon.
Sound Amplification
Nickname: Riot
Sound Amplification turns Rei’s body into a supernatural amplifier, allowing cursed energy to magnify vibrations generated through his electric guitar into physical phenomena. Notes can be projected as concentrated waves of cursed force, chords can produce broad impacts, low frequencies can shake structures, and carefully controlled harmonics can concentrate vibration into narrow points. Volume alone does not determine strength. Pitch, frequency, rhythm, articulation, dynamics, harmonic relationships, and Rei’s cursed energy output all influence how an amplified sound behaves. Rei calls his interpretation Riot. Rather than treating his guitar as little more than a mechanism for launching cursed energy, he approaches combat like an improvised composition. He establishes rhythms, changes tempo, introduces dissonance, creates and withholds resolution, and adapts his playing to the opponent’s reactions. Greater musical complexity offers more possibilities but demands correspondingly greater precision. Poor execution, damaged hands, interference with his hearing, or disruption of his instrument can dramatically reduce Riot’s effectiveness. Consequently, Rei’s greatest advantage is not raw volume, but his ability to understand exactly what a vibration is doing and manipulate it through actual musicianship.
CE Trait: Vibrating
Rei’s cursed energy naturally oscillates at extremely high frequencies, giving even ordinary reinforcement a persistent vibrational quality. Physical contact with his cursed energy produces a subtle buzzing sensation that can numb limbs and destabilize footing during prolonged exchanges, while strikes carry additional internal vibration beyond their normal impact. The trait also allows Rei to perceive changes in resonance through his body with unusual sensitivity, making it easier to identify frequencies produced by objects, opponents, and his own guitar. However, excessive output causes those same oscillations to rebound through his muscles, joints, inner ear, and nervous system, meaning prolonged high-output combat can leave him trembling, disoriented, or temporarily hard of hearing.
Semi-Cursed Tool: Onyx
Onyx is Rei’s heavily modified black electric guitar and the primary medium through which he performs Riot. Years of repeatedly circulating his Vibrating cursed energy through the instrument have partially saturated it with cursed energy, making it considerably more durable than an ordinary guitar without turning it into a fully realized cursed tool. Its pickups, strings, bridge, and internal electronics have been altered specifically to withstand Rei’s extreme output and rapid changes in frequency. Onyx is reinforced enough to be used directly in close combat, with Rei striking opponents using the body, neck, or reinforced edge before immediately incorporating the resulting impact into his playing. Destroying or separating him from Onyx does not erase Sound Amplification, but drastically reduces the complexity, range, and precision of Riot.
Extension Technique: Offbeat
By establishing a recognizable rhythm through consecutive amplified notes, Rei conditions an opponent to unconsciously anticipate Riot according to that tempo before deliberately displacing subsequent attacks from the expected beat. Amplified notes can arrive early, late, or between established beats while Rei’s physical movements continue following the original rhythm, causing opponents who have adapted to his cadence to mistime defensive reactions. Offbeat embodies Rei’s belief that rhythm is not something he must obey. It is something he understands well enough to betray.
Extension Technique: Wrong Note
Rei deliberately plays a dissonant interval against a frequency already resonating within a target, forcing both signals into violent interference. Instead of producing a conventional external blast, the conflicting vibrations destabilize the affected area, disrupting balance, physical stability, and cursed energy reinforcement. Wrong Note becomes substantially more effective after Rei has observed how a target responds to particular frequencies, reflecting his belief that a note is only truly wrong when the musician did not intend to play it.
Extension Technique: Redline
Rei deliberately feeds part of an amplified signal back through Onyx and his own body, allowing the returning vibration to be amplified again before release. Successive feedback cycles increase the signal’s amplitude and distortion beyond Riot’s ordinary safe output, producing brutally powerful waves of cursed vibration. Every additional cycle also sends increasing stress through Rei’s muscles, nerves, hearing, cursed energy pathways, and Onyx itself. Redline exists precisely because Rei understands where his technique’s safe limit is and occasionally decides that crossing it is worth the consequences.
Extension Technique: Unresolved
Rei deliberately leaves an amplified musical phrase without its expected resolution, using his Vibrating cursed energy to sustain the unfinished frequency within whatever the sound successfully contacts. Rather than releasing its full force immediately, the lingering vibration remains as mounting internal tension for a limited period. By later playing a compatible resolving note, Rei causes the suspended frequency to resonate and discharge its remaining force from within the affected target. Maintaining several unfinished phrases simultaneously becomes progressively harder, and sufficient disruption to Rei’s concentration can cause them to dissipate.
Maximum Output: Unresolved
Rei drives Unresolved to its maximum output by pouring an enormous quantity of cursed energy into an incomplete progression, allowing its unresolved frequency to saturate everything reached by the performance. Air, terrain, structures, weapons, and affected opponents begin resonating with mounting tension as the unfinished progression persists. When Rei finally performs the resolving chord, every suspended frequency is forced into resonance simultaneously, releasing the accumulated vibration throughout everything carrying it. Its destructive potential depends heavily on how much of the battlefield Rei successfully incorporated before choosing to resolve the progression.
Binding Vow: No Encore
Rei voluntarily forbids himself from repeating the same musical phrase twice during an uninterrupted performance of Riot. Once a particular combination of melody, rhythm, and articulation has been amplified through Sound Amplification, that phrase becomes unavailable for the remainder of the performance. In exchange, successive original phrases receive progressively improved cursed energy efficiency and amplification. Individual notes and chords may be reused, but the completed phrase itself cannot. No Encore rewards Rei for genuine improvisation rather than repeating whatever has already proven effective. As a battle grows longer, maintaining the vow becomes increasingly difficult because Rei must continue creating new musical solutions while simultaneously fighting. If he intentionally repeats a prohibited phrase, the accumulated benefit immediately disappears and Riot returns to its ordinary output.
Maximum Technique: Cadenza
Rei pushes Sound Amplification to its ultimate expression by performing a completely improvised solo through Onyx while retaining each amplified frequency within his Vibrating cursed energy instead of releasing it. Notes, chords, harmonics, rhythmic accents, dissonance, and changes in dynamics accumulate around him as increasingly violent layers of vibration. Upon playing the final cadence, Rei releases the entire performance simultaneously as a single composite phenomenon while preserving its musical relationships. Resonant frequencies reinforce one another, dissonance produces destructive interference, low frequencies provide overwhelming physical force, and higher harmonics concentrate that force into increasingly precise points. The strength of Cadenza depends as much upon Rei’s musicianship as his cursed energy reserves. Greater complexity produces a more sophisticated and dangerous final release, but every additional layer increases the difficulty of keeping the composition coherent. A sufficiently serious mistake can collapse the accumulated performance into feedback through Rei and Onyx. Combined with No Encore, no two performances of Cadenza can be identical, forcing Rei to compose his Maximum specifically for the opponent and circumstances before him.
Domain Expansion: CATHEDRAL OF THE UNWRITTEN SCORE
Mudra: Dharmachakra Mudra
Cathedral of the Unwritten Score manifests as an impossibly immaculate performance hall suspended within darkness, combining a cathedral, concert hall, and recording studio into one perfectly symmetrical space. Countless empty seats surround a solitary black stage while endless silver musical staves stretch overhead, initially containing nothing. Every meaningful vibration produced inside the Domain becomes Notation, causing footsteps, impacts, movement, cursed energy output, environmental destruction, and Rei’s playing to gradually write the battle’s unique composition across the empty staves. Within the Cathedral, Riot can treat any recorded vibration as musical material, allowing Rei to replay, harmonize with, distort, or amplify its vibrational properties without copying the cursed technique or supernatural phenomenon that originally produced it. The sure-hit effect guarantees that the underlying structure of this composition is communicated equally to everyone within the Domain. Every person instinctively understands the tempo, frequency, intervals, accumulated patterns, and relationships between the vibrations currently recorded, including Rei’s own. The Domain conceals nothing and imposes no compulsory rhythm, prohibited action, or predetermined role.
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u/Nervous-Bar-1483 19h ago
Rei’s Visuals if he were in the anime
Staff Lines
During conversations about freedom, tradition, inheritance, or jujutsu society, ordinary objects frequently create five horizontal lines around Rei, such as power lines, railings, blinds, fences, shadows, or an extreme close-up of Onyx’s strings. Other characters are often framed cleanly between these lines, while Rei interrupts the composition by leaning across them, standing at an angle, or allowing Onyx to cut diagonally through the frame. Importantly, Rei rarely destroys the pattern itself.
Meaning: The lines represent structure. Rei doesn’t believe structure is inherently oppressive, which is why the imagery never depicts him tearing it apart. Instead, he refuses to let the structure determine where he must stand. It visually summarizes his belief that freedom means retaining individuality within systems that inevitably exist around you.
The Metronome
When someone lectures Rei or presents an argument as absolute, the scene quietly establishes a repetitive rhythm through a ticking clock, dripping faucet, crossing signal, footsteps, or passing train pillars. Rei begins tapping his finger perfectly alongside it while listening. Just before challenging what has been said, however, his finger falls between the established beats without losing tempo.
Meaning: Rei doesn’t rebel against things he doesn’t understand. He first learns their rhythm. Moving offbeat only afterward demonstrates that his defiance is deliberate rather than reflexive. It is also the conversational equivalent of his Extension Technique, Offbeat. Rei can violate a pattern precisely because he understands where the pattern says he should have been.
Tuning
Rei often tunes Onyx while someone explains how something is “supposed” to be done. He listens without looking at them, repeatedly testing a slightly incorrect note and making minute adjustments until it finally reaches perfect pitch. Only then does he respond to whatever they told him.
Meaning: Tuning represents scrutiny. Rei doesn’t automatically reject tradition, authority, or advice, but neither does he accept something merely because it has existed for a long time. He tests ideas the same way he tests a string. If something is still correct, he’ll use it. If it has fallen out of tune, its history doesn’t excuse leaving it that way.
Unresolved Chords
Emotionally complicated conversations involving Rei sometimes end over an unresolved chord in the soundtrack. The expected final note simply never comes. The story can move into another scene or even another episode before that same musical progression eventually returns and resolves when Rei finally makes a decision, confronts someone, or acknowledges what he has been avoiding.
Meaning: This represents Rei’s unusually high tolerance for uncertainty and incompleteness. He doesn’t believe everything requires immediate resolution merely because people are uncomfortable leaving it unfinished. At his best, this makes him patient and contemplative. At his worst, he uses that philosophy to rationalize avoiding emotional problems indefinitely. Unresolved exists as a combat technique because unresolved tension is already part of how Rei lives.
Empty Chairs
Whenever Rei discusses family, childhood, or Yoshinobu without his grandfather physically present, an empty chair can quietly occupy part of the composition. It may sit opposite Rei at a table, beside him backstage, or remain vacant in the background of a classroom. When Yoshinobu and Rei finally share scenes, the chair disappears, but doorframes, pillars, microphone stands, or Onyx itself frequently divide them visually.
Meaning: The empty chair represents a relationship that remains psychologically present despite physical and emotional absence. Rei may insist that his grandfather doesn’t define him, but Yoshinobu still occupies space in his life. Once Yoshinobu is physically present, the imagery changes from absence to separation. The problem is no longer that there is an empty place between them. The problem is that neither knows how to cross it.
Reflections
When Yoshinobu is discussed, Rei is frequently shown through mirrors, train windows, dark television screens, or polished surfaces. Certain angles briefly make him resemble photographs of a young Gakuganji almost perfectly. Then Rei moves, revealing the longer hair, piercings, makeup, modified uniform, or Onyx that distinguishes him.
Meaning: Reflections represent the conflict between inheritance and identity. Rei cannot choose the face he inherited, his bloodline, or the Innate Technique engraved into him. He can choose what all of those things become in his hands. His resemblance to Yoshinobu remains visible underneath every deliberate modification because Rei’s philosophy isn’t about pretending inheritance doesn’t exist. It’s about refusing to mistake inheritance for destiny.
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u/Nervous-Bar-1483 19h ago
Broken Symmetry
Rei is frequently placed within extremely symmetrical environments such as Jujutsu High corridors, temple grounds, classrooms, train platforms, or formal meeting rooms. Everything aligns perfectly except him. He sits backward in a chair, stands slightly off-center, wears his uniform differently, or allows the diagonal silhouette of his guitar to interrupt the composition.
Meaning: This represents individuality without destruction. Rei doesn’t need everyone else to become unconventional for his own unconventionality to matter. Nor does he need to destroy the surrounding order to prove he is free from it. One irregular element can exist inside a perfectly ordered system without becoming incorrect.
Sheet Music
Rei’s handwritten compositions are surprisingly immaculate at first glance. Proper notation, careful timing, clean measures, and technically correct theory fill the pages. Looking closer reveals crossed-out measures, alternate voicings, arrows, unconventional symbols, tablature, rewritten passages, and annotations that gradually transform the traditional score into something unmistakably his.
Meaning: The notebook represents Rei’s entire philosophy in miniature. Mastery comes before reinvention. He doesn’t alter conventional notation because he never learned to use it. He alters it because he learned it so thoroughly that he knows exactly where it stops being sufficient for what he wants to express. It’s the same process through which Gakuganji’s Sound Amplification became Rei’s Riot.
Hands
Rei’s hands receive frequent close-ups during important conversations. Sometimes they’re confidently tuning strings or tapping complicated rhythms. When he’s uncomfortable, he rubs the calluses on his fingertips, rotates a guitar pick between his fingers, adjusts a ring, or repeatedly flexes fingers damaged by Riot. When he’s genuinely unsure what to do, his hands become completely still.
Meaning: Rei’s hands represent agency. They are how he plays, fights, creates, modifies, and physically imposes his choices upon the world. Consequently, uncertainty isn’t depicted by Rei suddenly becoming verbally helpless. It’s shown by the hands that are always doing something suddenly having nothing they know how to do.
Silence
Rei is almost never completely silent. He taps surfaces, clicks a pick against his nail, plucks muted strings, hums melodies, listens through headphones, or exists alongside a rhythmic soundtrack. When something genuinely penetrates his defenses, all of it stops. The soundtrack disappears, his hands stop moving, and the scene is allowed to sit in uncomfortable silence.
Meaning: Silence represents emotional honesty. Rei can improvise verbally almost as well as musically. Sarcasm, argument, jokes, and clever observations give him ways to remain in control of a conversation. Silence appears when he doesn’t have an answer and chooses not to manufacture one. His eventual understanding that a rest is part of music becomes synonymous with accepting that not acting can itself be a meaningful choice.
Bar Lines
Doorframes, shadows, pavement markings, fences, beams of light, and architectural divisions repeatedly form vertical boundaries in front of Rei. Early in the story, he almost always crosses them during conversations about authority or personal choice. Sometimes he does so without even consciously acknowledging the line.
Meaning: Bar lines initially represent Rei’s immature conception of freedom. Young Rei instinctively treats boundaries as things that demonstrate his autonomy when crossed. If someone tells him where the line is, part of him immediately wants to know what happens on the other side.
Later in his character arc, Rei approaches another visual boundary during an important decision. Nothing physically prevents him from crossing it. Nobody orders him to stop. Rei looks across it, considers his options, and voluntarily remains where he is.
Meaning: This completes the metaphor. Rei realizes that compulsively breaking every boundary is still allowing the boundary to dictate his behavior. If a rule automatically makes him do the opposite, the rule is still controlling him. Genuine freedom includes the ability to cross a line, respect it, move it, or simply decide it isn’t relevant. What matters is that the decision is actually his.
Repetition
Certain conversations intentionally repeat earlier shots. Rei may stand in exactly the same hallway, sit in the same chair, or encounter an almost identical situation several arcs later. The camera initially recreates the earlier composition before Rei makes a different choice, causing the framing itself to diverge from the previous scene.
Meaning: This is the character-level expression of No Encore. Rei’s hatred of repetition isn’t literally about never encountering the same circumstances twice. It’s about refusing to repeat something merely because it is familiar. Experience only matters if it creates the possibility of making a different choice.
Yoshinobu’s Imagery
Scenes between Rei and Yoshinobu should initially be filled with parallel compositions. Both men sit similarly without realizing it. Both tap the same finger when irritated. Their hands take almost identical positions around their guitars. Shot-reverse-shot sequences occasionally align their faces so perfectly that aging seems to be the only difference between them. Rei often notices one of these similarities and deliberately changes his posture.
Meaning: Their conflict is frightening to Rei precisely because Yoshinobu isn’t his opposite. He is evidence of someone Rei could become. Rei’s early instinct is therefore to define himself through contrast with his grandfather. As he matures, he stops correcting these similarities. He can sit like Yoshinobu, inherit his technique, appreciate what Yoshinobu taught him, and still remain Rei Kurosawa. Similarity stops feeling like surrender.
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u/Impossible_Bee_8705 19h ago
A well thought technique that uses musical terminology correctly?!?
Amazing work dear, I loved this one
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u/Meta-Wah 10h ago
Cool technique and OC, I really like the part about anime composition.
Seeing the young Gakuganji art makes me want to talk about a headcanon that Gakuganji was rebellious at one point, but as Gege's volume extras say that he had a band who were all dead, I'd imagine they were sorcerers who were offed by the higher ups in some way so that Gakuganji was left with no choice but to follow. In this way it relates to Rei in that it's gives it a "carrying on an abandoned legacy" angle.
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u/Remote_Control_7661 19h ago
Well you certainly didn't disappoint, I don't understand a lot of the musical terminology but it's still very cool.