I Finally Get to See Your Downfall: Five Years of Being Cheated on in a LDR With a Trading Company Man

"Hey Keisuke. I'm really looking forward to the wedding." Miyagi Prefecture, Sendai City. This is where our protagonists, Chiaki and Keisuke met and vowed to marry each other. After graduating college, Keisuke starts working at a big-name trading company in Tokyo. Doing LDR is a bit lonely, but Chiaki believes in the love they have. However... Keisuke changes after moving to Tokyo. Every weekend, Keisuke has vulgar affairs, and does nothing but lie to Chiaki, and the two stop talking. Things are miserable. But Chiaki put up with it. She knows about everything and stays with Keisuke for 5 years. And there are only three months until their wedding...

(Source: MangaPlaza)