He's half a monster, so most probably he grows up faster than humans, and why he seems so simple in his attachment to MC. He's still a young one, even if his body is enormous.
Im gonna say that he's a chimera zombie-hybird thing since he was still in the womb when his mom was bitten and turned into a mutant and it most likely corrupted his biology. He wasn't crying or anything when he was born, just staring at them like he was aware of what was happening around him. Imma assume that he developed faster but SPOILER...
considering how he was hidden away and treated my his only family, he's VERY oblivious to a lot of human knowledge and social cues which is why Im guessing he forgets that humans need to eat to survive and why he doesn't know anything about sex and so on. (〜￣△￣)〜
that makes so much sense guys thanksss, i hope we get more details instead of just sex huhu
y'all, can someone explain the timeline? i thought its just a few years when the zombies or whatever began? why is seme's backstory started already when zombies were around?