Obviously not.
Because, in the first place they are only fuck buddies... so he isn't cheating.
I'm reading so much yaoi right now that I was so confused by your comment, I thought this manga was either "Meeting him" or "Window to Window" XD
I could've sworn that they did clarify that they were going out but maybe I'm wrong. I have a bad memory and I'm too lazy to check. Anyway, I'm pretty sure that the seme's ex bf or love or whatever has only just now gotten in touch with him so the seme hasn't even had the opportunity to cheat. Also I doubt a character would cheat on his love interest in a BL manga just like how it's almost always safe to say that the main character in a shounen manga isn't gonna die.
Maybe more like unfinished business...like to cut that person off. That person might have been all up on him. Anyway you know how these misunderstandings go. I'm just set for some passionate love make up sex
Lol I know it's not cheating I'm joking people calm down.
Yea make up sex is always the key
Oh no......m he's cheating!!!!!