People who are disturbed by young girls being sexualized in manga must be new to manga/anime, lol... or have just really sheltered themselves... Anyways, who cares, as long as they're at least 13 or so... It's a manga; it's Japan.

i think rinne is the reincarnation of the maiden who met dragon god before

Nah that's not what got to me. More like, you would expect him to choose one of the three girls, and I was thinking this damn mangaka is gonna troll us and he's gonna pick the kid instead! 🤣