@SotiCoto one of those? Do you mean one of those that are disturbed by old men being attracted to 12 years olds?
It wouldn't bother me if a 500000 years old fucked 20 years old because 20 years old is already adult, but we were talking here about 12 years old.
A literal child, not some magical loli who lived for Millenium looking 12 years old (Which would still be disturbing) or anything. but a child, How is him being in a younger body changes anything? He lived for like 25 years. unless his body changes the way his mind works this implies that even as a 25 old he would still be attracted to 12 years old isn't it?
And why does what women in that world think even matter? Didn't he come there from our world Where he lived vast majority of his life?
Talking about Rudeus Greyrat, i read Mushoku Tensei's web novel roughly 5+ years ago so sorry if my memory is failing a bit but wasn't he like close 40 when he died and once he reincarnated he kept his memory, traumas, etc basically it's him just in a fresh body, and by older you mean which one? As far as i can remember all of his wives were his (physical bodies) age except for one who was older but looked like 10 yeas old child. so I'm not sure why did you think this is a good example for an excuse of such behavior because to me it's even worse for example. (Except in the story later it is explained that his young body affected his mindset and personality slightly so that does excuse Rudeus a least a little bit)
Just to be clear, I'm not talking here about legality of it, because you know... reincarnation isn't real so we have no dilemma over that, and protagonists in both stories are from earth, they lived vast majority of their lives here so its not question of common sense either.
Anyways i wrote a lot, English isn't my native language so i might've made some errors, i could write more but first, nobody would read a wall of text and secondly if this much won't change your opinion (which I'll be honest i doubt it will) then nothing more i wrote would.