Ah, thank you very much. In the first line the 「じゃない」 threw me off.
Kenichi is the one who says 「どーゆうことだよ こりゃ」 and I'm pretty sure Kenichi is the ex-boxer. I can post pictures of this scene if you want though I don't wanna nerdy
In the page where Sakaguchi says 「ちょっと 信じらんない！！」 Kenichi is beating on Yuusei who's passed out. She's pleading for him to stop.