@orb4eva Risako is absolutely worse than Reiichi. She intentionally and directly hurts Kaoru on multiple occasions for her own selfish reasons. The way it's looking, Reiichi felt pressured into getting together with Kaoru in some sort of desperate attempt to save her from total collapse. He was sacrificing the apparent happiness he had with Risako to make things work with Kaoru, only we know it didn't go as smoothly as I'm sure he was hoping. He clearly loves Kaoru; the problem is his love is probably not the same kind Kaoru feels for him, and Risako being Risako probably tempted him as she has been known to do.
To be honest, it's possible he hadn't even cheated on her yet and the whole thing was a red herring. It's possible that time he was caught with Risako, he was getting dangerous close to actually cheating on her, and that guilt trip he was going through when she ended up in the hospital, asking himself what the hell he was doing, makes some sense.
Really, Risako just needs to get hit by truck-kun and isekai'd to some fantasy land where she can build whatever gender harem she wants, and let the rest of the cast deal with their issues. We don't really need any sociopaths who lack a conscience.