Yeah, I felt sad for the MC. The story sounds more sadder than it is, but it did have very sad moments. All the characters were really funny though, and there was humor. But the older guy and the MC really do love each other. It's just their timing was never right. They just have a really long and complicated love affair.
Start with this! Beginning of the series http://www.mangago.me/read-manga/not_love/
This series goes over many years in the life of the MC. It starts by showing him as a homeless young man who is saved by an older guy who rescues him and let's him live in his apartment. The MC falls in love but the older guy refuses to touch him. Then the older guy's wife come back, they reunite, so the MC leaves and they separate for many years. Then the rest of the series just shows the MC older and hooking up with many, many different lovers. But he still can't get over the older guy, who's still married. The older guy and the MC meet again and they start hooking up, but he won't leave his wife. So the MC just continues to find new lovers, and then the last chapter ends with him finally asking the older guy to leave his wife and be with him. But we don't see the answer