Jump the shark chapter.
The author had to find a way to make Mizutani seem like a BAD GUY that he made her do something out of character like deliberately not help after Toame seriously injured his head.
This doesn't make sense because Mizutani loves seeing Toame feeling guilty or emotionally conflicted and obviously she won't be able to do that if he severely injures his head and possibly dies.
In reality she obviously would have tried to stop the bleeding or phone an ambulance, and certainly not ignored Namehata when she told mizutani to get something to stop the bleeding.
But no the author had to try and find some way to make Mizutani seem "bad bad bad"
Disappointing. The author should have had Toame acknowledge to himself that he liked being licked MORE while cheating and sneakily doing it around Mizutani, and that he LIKED having two girls fawn over him and asked them both to be his women . Yes, Mizutani wouldn't be interested if Toame is enjoying it and deliberately having a menage-a trois, but still she probably would have been willing to try it for a little while just to see if she could still squeeze out some guilt from him. Just one scene of him claiming them both as the climax as he realises what he actually wants would have been best.