I'm going to say it again, you have to actually read the story. You have to be involved with it enough to have a sympathetic, feeling reaction. you have to let the story give you a full understanding of where Kento Kirishima is coming from. It was a heartbreaking moment, and your soul should have been crying out for Kurama to come back, not be up in your brain, judging. You can't be completely without a spirit for this story. You can't just read parts and think about it. You have to connect with it. Only then will you understand perfectly why Kirishima asked Kurama to be lovers in that sad moment. If you'll recall, Kirishima literally cried the entire night after that. The author did a beautiful job portraying all this, so I don't get how you could have missed it unless you didn't read it.
The fact that he tried to ask him out after raping him......