I know you're being facetious here but why do people actually hate Kase I don't understand
For risking her exit from the dormitories in a race. But it's mostly a cultural shock. For us, occidentals, is quite easy to deny it, but in japan she had literally no option.
I'll try to explain it after living in Japan for two years for work.
At first she says "no" to Fukami (Just saying "no", even to a friend, is already a taboo in their culture ("Sontaku", 忖度)), even when she owes her a debt for having cleaned the room all year (duty and social obligation, "On" and "Giri", 恩 & 義理). Inmediately the other girls bursts into the room, pressuring her ("shakaiteki atsuryoku", 社会的圧力). And to top it off, Inoue bursts in and forces the race with her senpai authority, something unavoidable in group dynamics like work or sport teams (relation "senpai-Kouhai", 先輩・後輩) appealing to the harmony group ("wa", 和)
And yet, in "Fukami and Kase san: Part 1" Kase sets the ground for leaving the dorms anyway if she loses the race, telling Fukami that she will explain why she is leaving if she loses. Carrying a very strong social stigma for breaking her promise (haiji, 恥).
The race was never a problem for Yamada, even Mikawa (who is usually ruthless towards Kase) reacted with concern for her.
If something is not realistic in that arc is that Kase would have stopped being friends with Fukami for bringing problems to her daily life ( the "Meikawu" 迷惑 that causes "En o Kiro" 縁を切る), but since Kase is a hopeless idiot she wouldn't break bonds with teammates.
In Japan, this arc has been fairly well received by critics and readers. Their biggest complaint is that it's about time for Kase to step forward and come out of the closet. Another challenge in Japan