To be fair they were like 10 so i dont blame them for forgetting i cant remember all my childhood memories either tho i do remember my important friends it could be that it all happened in a short amount of time tho
aside from age, I think right after this MC was under a lot of pressure and anxiety bc his parents discovered he was faking going to the taekwondo classes, that probably made him kinda blank out that period of his life (i had something similar happen when I was 8/9 years old)
It's just normal, I even couldn't remember completely what I did yesterday, let alone childhood memories ╮(￣▽￣)╭
There are still so many unanswered questions... like why did mc forget his childhood memories with ml???