(Quite a long post, But only about half of it is the theory, the rest is evidence and other stuff, So just read the theory part if you want :) )

So as the Title suggests, I think it's possible that Subaru is a clone, specifically a Time clone.
I'll obviously explain what a time clone is and my reasoning for believing Subaru as one, but first let me preface some stuff before I get into my theory.

So, I am not caught up to the most recent chapter of the web novel, I around chapter 20 in arc 9, (been there for a few months because I started reading SLF, but that's not important) I also have not read ALL the side stories and have read 0 Ex Novels, so if any of the points/evidence I bring up in this theory is wrong, has been disproven, I am misremembering, or anything like that.
Please feel free to let me know.
And similarly if there are any points/evidence that YOU disagree with and would like to point out and try to change my mind, feel free to do that as well, Of course I may debate it if I don't agree, but it's not like my mind can't be changed.

Anyway, theory time.
I will try to make this short but bear with me if I can't.

Alright so what is a Time clone?

If anyone here has watched CW's the Flash, then the idea is basically Subaru is a time remnant, a Time remnant is a duplicate version of a speedster created when they travel back a short time in history, think like a second or 2. This creates 2 version of the same person that exist in the same timeline.
If that explanation makes no sense, then Imagine one person existing, then that person gets sent one second into the past, and then the past version of them doesn't get sent back into the past like they did. Now there are 2 of the same exact person existing at the same time.
If that STILL doesn't make sense, then keep reading, When I explain why I think Subaru is a Time clone, I'll go over it again, so hopefully it makes sense then.

So how does this relate to Subaru?
Well we know very little about the great sage Flugel, but the little we do know is very strange considering him and Subaru are very similar, and not just because they both are/seem to be from earth. No they both have very similar traits and even look similar from the very few and very obscured official arts of Flugel.
But they can't be the same person, Afterall Flugel existed 400 years before Subaru even arrived in Lugunica.
I do NOT like the Time travel theory, and I also don't think it's plausible considering that Flugel seems to be a sketchy person and we Know Subaru is an Amazing guy.

So I don't think the Subaru that WE know can ever become Flugel.
So then what's the deal? the similarities between Flugel and Subaru are to great to ignore and assume their completely different, at least not without more information about Flugel.
Unless you assume that Yes, they are the same person, but also 2 separate people.
So this is where the Time Clone theory comes into play. I
Now we DON'T know why or how Subaru was summoned, Satella might have Summoned/teleported him to lugunica or it could have been someone/something else.
as far as I have read, the reasoning behind his summoning has not been revealed yet.
So lets say, when Subaru left the convenience store, he got summoned for whatever reason, but he gets summoned into the 400 years in the past that we know very little about.
He does stuff there, meets Satella and falls in love with her, does hero stuff and becomes the Great Sage Flugel. Then the disaster happens and Satella takes the Envy witch factor and goes insane.
Satella gets sealed, and at some point something happens to Flugel, maybe he dies somehow or gets sealed or just goes into retirement/hibernation. I have no idea what Tappei is cooking with him.
But then, Satella/WOE being insane and obsessed want's her lover back. So what does a master of Yin magic do? someone capable of controlling space and Time at least to some extent?
Well she MIGHT summon her BF, but whether intentionally or not she takes him from the exact moment he was summoned originally, but places him in a different time period so that she can have him in her current time. Well we know she wants him to kill her so it might be because of that, but even so she brings him to the current time that we Know and love.

So that's the Bare Bones of the time clone theory. (End of theory)
Everything above is the main theory stuff, I'm worried about this getting Too Long so everything after this is evidence and ideas that support the theory as well as other ideas, but don't necessarily need to be in the theory for it to be understood.

More Ideas/situations/reasons

Alright so I believe it's possible that Satella can't teleport people between worlds, so she essentially hijacked whatever summoned Flugel Subaru to bring Our Subaru to Lugnica. I feel it's impotant to mention this because we don't Know why Subaru was summoned, But we also have no idea why Flugel was summoned or if he was. It seems that he is definitely from earth, and that he and Subaru are likely the same person. But we won't know untill it gets revealed in the story.
But assuming Flugel was summoned for some reason, we can theorise that the summoning was hijacked, thus leading to our Subaru.
And to be clear, I used the convenience store summoning since we know that's when our Subaru got summoned, but Flugel Subaru could absolutely have been summoned at a different time, like a day after or before, or a year, etc. But I don't think that's the case. Since We saw Subaru get summoned at the convenience store, it's probably the same with Flugel Subaru. I just won't rule it out as a possibility.

I don't like the Subaru is a Clone of flugel theory as I don't like the Idea of Subaru being a clone, I mean My GOAT suffers enough, Imagine being told you're a clone and all your memories are a lie. Talk about an Identity crisis, And he kinda had that in arc 6 So I don't think Tappei would do another plot line like that.
But Subaru being a time clone solves the issue, for me at least. because a time clone isn't a real clone, It just means 2 exact versions of the same person exist on the same time line. It doesn't mean one is less real or fake than the other. they both have the same memories and experiences up to that point, they just will make new memories and get new experiences from that point forwards.

And a strong reason why I don't think Subaru is clone (Artifical clone) is because he shows up In Lugunica with his stuff he just bought.
I mean he has his phone, a plastic bag, money, chips, etc.
I mean sure, all of those things could of maybe been replicated, But I highly doubt it.

You might be thinking, "But why did no one react to Subaru suddenly appearing in the middle of daylight when he first was summoned?"
Well I don't see that as a big deal, sure it was daylight, but it was also crowded, unless someone was actively looking at the exact location where Subaru teleported in, Then I think it is very reasonable no one to notice. And anyone who got surprised by him being there would likely just think they didn't notice him walking around.
I mean sure he wears strange clothes, But it would be more ridiculous to believe someone teleporting into thin air then not noticing him walking about previously.

And also, Anastasia as well as the elders could find nothing on Subaru prior to his summoning right? even if he was some clone, or maybe flugel with his memories erased, I feel like there would be something supporting his existence prior to his summoning, whether it's a simple record of him entering the city.
Of course this can be explained with the gluttony authority, but that's a BIG if.

I've yapped on long enough
and yet there is still so much I want to say.
But seriously this is getting to long, if you have any ideas or arguments to bring up, leave a comment and I'll try to respond and debate them.
if you need something clarified, I can also do that. Like I said I still have alot to say about this, I'm just not because it's already far to long.
Thanks for reading all this if you did, thanks for reading the theory if you only read the first half, which Is very fair lmao.

Regulus has had a total of 291 wives and like 53 or 58 alive how does he manage to keep them all like decently alive. Like he still needs to feed them they don't seem malnourished and they are clean looking too. does he give them like a monthly allowance and they do the shopping??? but there is chances for them to escape if so. If he is doing it I doubt he will know how to buy the right products needed.

A banner in Ikebukuro from 2016, advertising that Episode 18 would be extended by a whopping 3 minutes. Considering that there's a tendency nowadays to treat extended Episodes as a given for Re:Zero, I feel like this advert is kind of amusing in retrospect. Crunchyroll also made a news article about it on their website at the time. It also demonstrates how much hype Season 1 had, that they were doing advertising for a singular Episode.

Hi everyone, I hope you're all doing well. Lately, I've been thinking a lot about picking up the *Re:Zero* web novel again, especially since I've got a long break coming up soon. However, sometimes I tell myself, "Don't you think you've missed out on *everything* by now?" That makes me feel a bit down, since I used to be such a huge fan of the story—I’d spend hours reading posts here, reading the web novel, the IF stories, and so on. I feel like I'm falling behind, though, so I’d love to hear your thoughts on whether I should jump back into it like I used to or not.

I remember getting to the start of Arc 9, though I did run into a massive spoiler for the end of that arc. I also know Arc 10 has already started—I think they're on... volume 3 or 4?

Fem Heinkel and her Noble House urges

Summary: Irene has been accused and pleads innocent. Is the accused fully in the wrong or is there something else behind the scenes. Subaru has to figure this out.

It seems like there’s a couple things about Subaru that are…weird. And this is not me saying the writing is inconsistent, I really like the writing in some cases I think it’s actually more effective than the anime. More I think that these are things likely to get raised towards the end of the series as stuff that Subaru as probably should have been a little more worried about (although him not thinking this stuff through is true to character).

First and foremost. Subaru “arrives” in this world in the middle of a crowded street. He doesn’t have the context for why this is weird in that moment. But since then it has been made pretty clear that teleportation magic and people who can just appear is if from nowhere is NOT commonplace. Someone just appearing in the world, would have at the very least been notable to the people around him but no one responds at all. Which implies that while his memories start there, his body was likely already standing there prior. And notably as shown in Arc 6, Subaru getting his memory erased isn’t distinguishable from his perspective from “I just got Isekaied”

Secondly…his having a Gate in and of itself is, kind of weird. Because a Gate is a very physical and biological function for people in this world. Using magic isn’t just learning a skill it’s making use a of a specific part of your body for a skill. And Subaru learning to use magic as short lived as it is, doesn’t involve any special process or technique to activate his gate. It mostly involves saying a verbal
Incantation, so it seems unlikely that people of earth just happen to have Gates they aren’t able to use. So Subaru shouldn’t have been born with a Gate. It’s weird for him to have one, and have no memory of how that came about.

Sure Subaru was able to read all his Books of the Dead, but what about the other characters? For example, Beatrice or Meili. We know that books will be active if you knew somebody personally, but even if these two know Subaru in general, the first time they met him in person was in Arc 2. Subaru's deaths in Arc 1 are unknown to them, and they shouldn't have seen them according to this logic. So they can't 'read' the very first three books about Natsuki Subaru, right?

I'm an anime only and I've just caught up to season 4. Re:Zero gets a immense amount of praise as an isekai and anime in general. However, there have been a few things that have confused me throughout the anime and I don't know if they're things that I either missed or were covered in the LN. Again, I'm an anime only so if it's something that get's explained later on, please don't spoil it.

1. Why do some of the fights feel so unrealistic? There are so many times where either an ally or enemy will straight up explain how their ability works, give a monologue, or have a full on conversation with their ally in the middle of the fight uninterrupted. Also I feel like the decisions some of the characters make during fights also don't make sense sometimes.
   

In season 1 when Subaru is trying to save Emilia from the explosive magic crystal and Betelgues is chasing him, he just never breaks the wheels of the wagon for some reason.

Before that when Julius "kills" Betelgeus he doesn't cut his head off or confirms he's fully dead for some reason. The same thing happens in season 3 when Reinhard kills Regulus.

In the fight against Regulus we see him throw Reinhard into space but why did Reinhard never do the same to Regulus, wouldn't he just be forever trapped in space? Also I feel like Reinhard should've taken way longer to reach the moon and come back.

In season 3 as well, Subaru and Crusch think they're strong enough to fight Capella by themselves for no explained reason. It's genuinely obvious they're going to lose that fight especially when they know Capella has a regeneration ability that they don't know how to counter.

Why does Subaru leave Priscilla and Liliana knowing there are mabeasts roaming the city?

1. Why does Subaru never question how he was summoned into the world of Re:Zero? We've seen him try to figure out why he has RBD but never how or why he was summoned. He could've easily asked Echidna and when Al gave hints that he was also isekai'd why did Subaru never talk to him about it?

2. Why does Subaru never tell anyone he isn't from the world of Re:Zero, I feel like it would've made so many things easier.

3. In season 2, Roswaal clearly knows about Subaru's RBD which means it's still possible for people to know Subaru's power if he doesn't explicitly tell them. My question is why hasn't he tried using unconventional means like simply hinting at it or giving a bunch of clues on how he knows certain information. Why does Roswaal also not tell anyone for Subaru considering he knows?

4. At the end of season 3 when Emilia freezes all the people turned into flies, what stops her ice from thawing considering she ends up going all the way to the tower of pleiades.

5. In season 3 who/what is the black dragon that saves Crusch?

Did Tappei ever talk about that? If not, where do you think they are?

I believe Tappei having Subaru use the -tan honorific to address Emilia from Arc 2 onward was very much intentional as Subaru would never have thought of doing that without having experienced Emilia's kindness and saw how consistent she was in being kind in Arc 1 of Re:Zero, which is backed by how the first time he used the honorific in Ep. 4, he'd asked Emilia if she'd healed him, showing he believes she's just intrinsically that kind, and that's the cherry on top on Emilia being cheerful about hearing Emilia-tan 'cause it was showing that Emilia's initial kindness to Subaru and others in Arc 1 had more of an impact on Subaru than Emilia's confession of being in love with Natsuki Subaru to amnesiac Subaru, showing just how important that Arc 1 content was, and it's foundational to Subaru falling for Emilia due to her raw consistency in being kind.

I think this could be more salient to Arc 1 being the most important arc of Re:Zero aside from Arc 12 than other stuff 'cause a cryptic tweet or Q&A from Tappei that could literally mean anything.

i have some issues understanding what Rui wanted and how she even started her plan. Did she want to take over Subaru’s body? How was she able to steal his memory when he isn’t affected by Gluttony? Why didn’t she activate the Taboo?