Manga series need childhood-friend ruination insurance...Inside of you is two wolves. One is Hina, childhood friend Genki big boobs best girl. The other is Fin, the karate asshole.
So long as Hina still exists as a character, I can tolerate Fin as a temporary gag. But if Fin is the new permanent Hina that's awful. Like buying a new car and it explodes as soon as you drive it off the lot.