Can someone help me find a manga

I don't remember EVERY detail since its been years but I'll try to be as detailed as possible:

A guy who was dating his long term girlfriend moved to Tokyo without her to finish his studies or find a job and when he moved into his apartment he met his older female neighbor who was married(I don't remember if she told him or he found out later) and later he and the neighbor slept together and he lost his virginity(his girlfriend wanted to wait I think) and at first he did regret it but he continued sleeping with his neighbor without telling his girlfriend. Later on (I think a few months to a year) the girlfriend visited the guy and she wanted to lose her virginity to him (and I think she did) but later on the girlfriend found out the guy and neighbor had been sleeping with each other but she decided to stay with him and he was happy because he thought she loved him even with his flaws but the girlfriend got extremely paranoid thinking the guy was cheating still and after a while she broke up with him.


Thats all i remember