Guess its more played for laughs here but IDK friend or not I'd be pretty annoyed at my childhood friend's behavior towards my significant other if I was her but that's just me I guess.
Mangakas, please! Stop with this bullshit trope! They are not entertaining and just makes both the MCs look bad. Stick to typical rivals. And if you don't wanna be hypocritical, add a gay guy rival instead. They're far more entertaining than the lesbian rival.
They have childhood friends not win as Female Love Interests for the Male MC. They have childhood friends as Lesbian Rivals for the Male MC. They just can't win at all.
I think hentai is where childhood friends keep winning.
Oh, the new character is annoying-maxxed. Mizuki seems unbothered, but I would have flipped my shit. Is it the patience of a saint? Or the ambivalence of a sociopath?
I despise such annoying side characters, they bring nothing to the story thats not unnecessary and annoying. Also they have a tendency to fall for the MC which is even more annoying.