A weird head canon developed while I read this.

I sort of developed this fantasy where say Sakai goes away for a couple of weeks for work or family stuff or whatever.

At first, Nishimura and Kitada leave each other alone, sticking to their own apartments, but Kitada's day off from work rolls around and he gets bored. So, what better to do than to go over to Nishimura's apartment maybe bully him a bit? He decides to bring some cold beers and a rented movie as a peace offering and at first Nishimura doesn't let him in, but caves when he finds out that the movie is that new one by his favorite director that he hasn't seen yet (lucky guess on Kitada's end).
They start drinking and Nishimura is really into the film. Kitada catches himself finding the other man's behavior endearing and almost sort of cute. He blames the alcohol. As the movie raps up there's a sex scene that's not too explicit, but leaves enough room for the imagination. Both of them are feeling their fourth beers at this point and the room settles into an awkward silence with a dollop a sexual tension.
Nishimura tries to stealthily take the disc out of the DVD player without the other man catching a glimpse of his not-quite-erection. Unfortunately for Nishimura, Kitada is a sharp motherfucker. Smirking, Kitada (only wanting to tease the other man) suggests that he "help" Nishimura with his "problem". Nishimura sputters defensively, claiming that he wouldn't get hard over something so minuscule if he'd only had the opportunity to get laid in the last couple weeks. Kitada teases him more, but drunkenly let's the word "cute" slip. Nishimura get even more riled up and goes to swing at Kitada (who's sitting, Nishi is kneeling), but loses balance and falls on top of the other man instead. Pushing himself from the other man, Nishimura realizes that he's not the only one with a not-quite-erection. He tries to tease back, but Kitada just agrees with him and bucks his hips up. Friction ensues, Kitada flips them and both of them end up having a drunken grinding session.
The end.

And perhaps this improves their relationship.