The situation is not even the same. When ootaki got slapped it's because yakushimaru was mad upset that he's being intimate + doing karaoke with some other girl after confessing to her. There's no reason for ootaki to slap her for joining a handicraft club full of girls and talked to girls her age.You know what he should do? He should slap her! Then it'll be exactly like how Yakushimaru acted! Ugh...