Isn't he both ? Why does he act like he needs to prove he's not rio but rather his past life former japanese-self? Japan master race or something ? Because in that world, his mother and father, though he's an orphan now, are natives of that world just like him. The fact that experience never takes over memories in all these manga makes zero sense. It's like you can't feel the weight of living in a different environnement. He regained memories of his past self ? The way he acts is schizophrenia and not a rational being who's recovered part of his memories, even if you're conflicted, you'd rather think about who you are and what and how will it change you.