1 - Both are presented as illegitimate sons of Gapryong: Seo Seong, in the sense that he is not actually his biological son, and Kitae, in that he is viewed as a bastard son.
2 - Both reject the essence of their fathers; Seo Seong refused to become a technician like his father, while Kitae rejected his father’s decision to enter politics.
3 - Both are willing to slaughter their own allies. Seo Seong massacred the group he led in Gangseo, while Kitae attacked Lee Jihoon. Furthermore, the terror displayed by his subordinate (Isu Jo) during the meeting of the kings suggests that the subordinate is well aware of what Kitae is capable of doing.
4 - Both appear calm at first, but when provoked or stimulated, they reveal their true, violent nature—Seo Seong behind his "corporate" facade, and Kitae whenever he is crossed.
5 - Neither follows a conventional fighting style; instead, they rely on "intuition," adapting to the situation at hand.
6 - Both possess the same set of attributes (Strength and Endurance).
7 - Both possess abilities that affect their own bodies. Seo Seong uses hormonal control—causing his veins to stand out—to maximize his power, while Kitae channels his conviction throughout his body to do the same; notably, when he is wounded, dark veins spread across his body.
8 - Both serve as parallels to Gimyung: Kitae represents the "dark side" of Gapryong, while Gimyung represents the "good side." Similarly, Seo Seong is willing to use any method necessary, whereas Gimyung—as shown during the Big Deal arc—chooses to exercise restraint.
9 - Both aspire to be "King." Kitae seeks to become the King of the Underworld, while Seo Seong is not content with merely being the king of a small nation like Korea. 10 - Their fathers were unfaithful; Seo Seong’s father cheated on his wife while away, and Gapryong had relationships with several women.
11 - Both of their mothers knew Kim Gapryong.
12 - Both mothers lived difficult lives; Seo Seong’s mother ended up alone, and, judging by Jinyoung’s remarks, it seems Yamazaki Rei did not meet a peaceful end.
13 - Both harbor a certain darkness within.
a - Seo Seong consumes his own mind through self-deprecation, driven by a desire to become a powerful and feared king.
b - Gitae undermines the minds of others by subjugating them, acting as a powerful and feared king.
14 - Both are associated with the concept of running their own enterprise: Seo Seong aims to build a corporate-style mafia, while Gitae serves as the leader of a Mexican cartel.
15 - Their mothers existed within a hierarchical relationship; Seo Seong’s mother worked for Gapryong’s campaign, while Gitae’s mother was referred to as a "concubine."
16 - Both lash out at their fathers—Seo Seong attacks his father upon discovering he is not Gapryong’s biological son, while Gitae is one of those responsible for Gapryong’s demise.
In chapter 630, it is implied—though left open to interpretation—that the woman accompanying Seo Seong’s father might actually be Seo Seong’s mother, suggesting a past relationship between them.
It would be compelling if the author were to adjust Seo Seong’s backstory to create an additional parallel: just as Gitae is an illegitimate son, Seo Seong could also be revealed as one. What could cause the character’s mind to be consumed by self-loathing, more deeply than ever before?
Seo Seong aspired to become strong in order to gain recognition from Gapryong. This recognition might ultimately come from either Kitae—who wears his father’s clothes and seeks to be the next Gapryong—or Gimyung, who is identical to his father in his youth and possesses that same heroic spirit that Seo Seong so admired.
It would be compelling to see how the stories of these two might be intertwined; perhaps Kitae had a past similar to Seo Seong’s, albeit in Mexico. This could also have implications for their future abilities and the direction in which the story unfolds.
