manga name pls help me!

What's the manga name of the boyfriend cheating on his longtime girlfriend with his neighbor.

The two mc has been in a relationship and like they were in a provincial/rural area in Japan, then the after they graduated highschool the boy decided that he wants to leave there and go to Tokyo because he is fed up by their little town, leaving his girlfriend there but promised to stay in touch with her.

Then he was loyal at first but he cheats with the lady next door. I also remember that the girlfriend found out because she followed him to Tokyo and said that she will also be studying there.

If I can remember, the girlfriend even got into some accident after knowing it, it only has 30 chapters as far as i can remember.