Yes, well it's not absolutely necessary, there's no rule about it, but it's a gesture of politeness to other readers to others by adding that to your comment if you wish to talk about things that have not been known by a majority of the readers reply
Is there a different Killua I don't know about? And if it's the same from H x H, then he's a character guys, aged up characters are a thing in fanfics since most anime/manga charas don't get to grow old in canon. They're fictional characters.
And your mom is awesome so don't freak too much. Mine would probably disown me. reply