Wow that was long
STOP!.. This reply has (too) many spoilers from the prequel so... Yeah... Stop here if you haven't read it.
I read the prequel and honestly I didn't see Kyouya doing anything that bad to Homura... He didn't force him, didn't rape him, didn't treat him badly... Just showered desperately him with love. He was so in love with Homura that he became desperate...yes, he tried to blackmail him once, but that didn't work out, so instead tried to approach him with a gentle touch. He's the pushy type, so he can't help but express himself when in love.
He was in love with the boss from the beginning and Homura toyed with him, starting from (falsely) promising to date him if became No.1 host.
And even though Homura knew about Koyuya's feelings he used them and took advantage of him because he felt Touji abandoned him, used him as a replacement for his broken heart and Kyouya, as the lovesick fool he is, took the opportunity to be with his beloved, he thought that that would finally be his chance. Because both of them thought that Touji was getting married, so Homura was technically single, from their pov.
When Kyouya realized that no matter how much he loved Homura and no matter how many heart warming promises he made, his love would remind unrequited, so he let go, even though he loved him so much, he let go... So I don't know why people see him as a villain who doesn't deserve his happy ending ┑(￣Д ￣)┍
Hah, I have an even longer rant on (the first page of) the prequel that explains in excruciating detail why what Kyouya did was terrible. (๑•ㅂ•)و✧
A nice redemption arc can be really gratifying to read, but Kyouya doesn't really make up for the horrible things he did to Homura in the previous story here. No, things have gone well for him despite his bad behavior in the past, and then he has the gall to be a hypocrite about it when he mentally criticizes someone else for things he himself did in the previous story. Sigh.
In general, it's really hard for me to get behind this relationship for a few reasons.
First, Kyouya changes love interests so often, as if only a modicum of kindness is needed for him to be "in love". It just didn't feel like Kiriya was special in any way, he just happened to be around and did something for Kyouya once (and he wasn't even particularly nice about it either). Like paying attention to him, even negative attention, is all that's required.
Meanwhile, Kiriya is such a crank most of the time, and doesn't act interested in Kyouya at all until very late into the story, which felt horribly rushed. I don't know how the author could've conveyed this better within the story while staying true to Kiriya's character. Having people around the periphery comment that "oh, he never lets people visit his house" or whatever seems like a cop-out, rather than doing the work of putting it in their interactions on-screen. I mean what's the point of an adult, a professor, bullying a student by ordering him around doing menial chores to begin with? Is he a sadist? Was he just lonely? If so, why hadn't he done this before to some other student in the 5 years since Ooura died? Why now? Why Kyouya specifically?
Also who was that woman he made mad at the cafe in the opener? Why was she never mentioned again after she disappeared off-screen? Is he bisexual? Were they dating? Was she a student that wanted in his pants but he told her no? If so, why would he even meet with her? Don't put something in there if it isn't going to tell us something his character. If he's gay, he wouldn't be there arguing with a woman that seems like his girlfriend. Make it a guy instead. Or make it Ooura's wife; he might have a reason to both meet with and argue with her, as we will find out later.
Also, as an aside, I couldn't figure out what Kiriya telling Kyouya to push down cafe owner was meant to convey about Kiriya's character. It was completely unrelated to his past. The guy Kiriya was in love with from before (Ooura) was already in a relationship with him when he told Kiriya he was getting married, which is a completely different sitch from the cafe owner being an oblivious married bonehead who is too nice for his own good. It's not like Kiriya having sex with Ooura after he was married was going to make Ooura any gayer, meanwhile Kyouya having sex with cafe owner might make cafe owner realize he (cafe owner) was gay or bi I guess. Was he trying to sabotage Kyouya's crush? How childish, if so. I suppose it could've been to show how Kyouya has changed, and would never force himself on anyone ever again (like he did with Homura), but even after he told Kiriya that's a jerk thing to suggest he do, he goes home and does it anyway! It was just a weird one-off that didn't add anything besides giving Kyouya a reason to be kicked out of his current residence so that he'll be forced to shack up with Kiriya. It actively detracts from Kyouya's character, which is bad.
It also really felt like there needed to be a point in the story where Kyouya just up and left DG-style, tired of putting up with Kiriya's standoffish BS, which would force Kiriya to exert some effort chasing Kyouya. And while he did leave, it wasn't because he chose to, it was because his mom collapsed or w/e. Weaksauce. Make it a choice on Kyouya's part, and it becomes a much stronger action. Also, it was a pretty unsatisfying development either way because Kyouya just let Kiriya's nonsense go immediately when he popped out of the car (how did he even find Kyouya standing outside the grocery store of his hometown?), as if he just had to accept the burden of the seme's bad behavior like so many ukes are forced to do. Ugh, no. Have Kyouya be reticent, and make Kiriya have to reach out to him first this time.
About the only surprisingly good things here are that Kyouya's a seke, and they both have armpit hair. (〜￣△￣)〜