Very good points and I definitely felt all of that too. The rape especially got me really confused like akamine regretted it but there's not even any reason given why he did it in the first place, people don't get shitfaced and aggressively assault other people like that for literally no reason, like he didn't just rape him he freaking threw his face into the ground like a fucking animal, that's some fuckin misplaced anger and resentment we need to be hearing about, and as you said it doesn't make sense for his character, it was just super out of left field and left unexplained.
Exactly like I get akamine had some dark thoughts like raping his roommate at one point but just a violent thought doesn't lead to that when you're not a violent person in general. If every drunk person was a potential rapist then.....
This manga was a bit mid for me let me explain. I felt some parts of the plot were very weak...like get shitfaced drunk and raping someone is not a thing when you're a nice or even a decent person. I wish akamine was portrayed more like a scum person bc this made noooooo sense and it felt very random just so it could kickstart the plot. When did utsumi started being head over heels with akamine? The timeframe of those events is veey vague and doesn't make much sense...and lastly fro them to bond like that.... They didn't have enough time together for their feelings to seem real. It needed better timing and better excuses for why some things were the way they're.