I get what you mean but it begs the question. is he 13 or is he 30?

he stopped emotionally maturing when he became a hikikomori as a teen in his previous life. he also has 30 years of life experience.

so a better question would be, is he 13 because he failed to emotionally mature past that, or is he 30 because he has that many years of life experience and wisdom?

if he’s 30 because of the experience, then would that same logic apply to a child that can show that same experience and wisdom?

if he’s 13 because he’s been reborn in a new world then what’s the problem with him flirting with another kid?

what if a child were in a coma and woke up 20 years later? would they be 13 or 30? would they be faulted for being attracted to teenagers or adults?

my point is, the show is a work of fiction that proposes some very deep thoughts on multiple subjects. if you can’t see past “old man pedo” you’re missing out on a vibrant story of characters and world building that honestly has no equivalent. it’s a great show with wonderful animation and I’d recommend it to anyone.