Shin Dousei Jidai

Satoshi started living together with Misako, whom he met two weeks prior while trying to pick up women. Life was going well for Misako, and she was happy to live with Satoshi as if they were husband and wife. One day, however, Satoshi finds a picture of Misako in marriage photos with a man he doesn't know... What is love? What is cohabitation? This is a story of men who could not grow up, and women who could not help but love them.

(Souce: Shogakukan, translated)