There is a perfectly reasonable explanation for everything, and don't think Ban won't break your face, got it?
1. The school girl outfits were a disguise, got it? So shut up about that.
2. That whole love hotel incident was part of a job. They were investigating. Not... you know.
3. When they rented that room for a few nights at that grungy motel, the single was cheaper than the double, that's all there was to it. And if Ban woke up in the middle of the night kind of - close - to Ginji, well, the A/C was busted and it was like a fucking freezer in there. And maybe Ginji's head was nestled just a little too comfortably in the curve of Ban's neck, but that guy did all sorts of crazy shit in his sleep, so that meant nothing.
4. So maybe Ban did just settle his chin back against Ginji's head after making sure he was really asleep. So what? It was cold, damnit.
5. Look. When they woke up. That was an accident, okay. They are both young, healthy, red-blooded males, and these things happen. It's a natural response! Little Ban and Ginji Juniors have minds of their own, and if they stand to attention when another body is in close proximity, it doesn't mean anything if the other bodies in question happen to be each other's.
Hey, what do you think you're laughing at? You think you can call the invincible Midou Ban-sama gay and get away with it? Yeah, fuck you too, buddy. Fuck you.