And let's all bear in mind the casual depiction of date rape - the guys roofied the girls' drinks to fuck them, right at the start. That's fucked up too. This is Harada, after all. Even if it's not an intense psychological story, Harada drops the heavy shit like it's no big deal... but if you think about it it'll reeeeeally mess with your head.
http://www.mangago.zone/read-manga/yoru_to_asa_no_uta/mf/c001/17/
Here, bottom middle panel when blondie's talking about "prep work" to do before the girls come up to the room. They also had the heating cranked up so the girls got flushed and hot - and Asaichi and blondie look at each other like "Yup, time to start." They're seriously predatory. Like I said, Harada just casually bringing the fucked-upness!
I think the reason the rape in this bothered people more than others is because it was depicted so realistically. It was sad and gross and Asaichi hated it and was terrified.
I've also seen people mention that it was unnecessary to the story but I would disagree, that was the turning point of his personality. He realized then that he was treating Yoru the same as he was just treated and that it was terrible. And then he is saved by Yoru and i think he confronts his feelings more after that. I just wish the rapists wouldn't have casually shown up here and there through chapters as if they didn't just do something that horrendous. But anyway, enough rambling, I LOVE this manga and I'm so happy it got a sequel! The way Asaichi looks at Yoru warms my soul and cures my depression. (づ ̄ ³ ̄)づ