Hatsukoi no Kanata

Ch 1-3:

His first love was his father's lover. To deal with this unrequited passion he made a habit of serial-dating older women. But then there's his carefree-but-straightforward friend Shinri, who remains sincere to an unrequited love. For the first time in a long while, this cynical young man's heart begins to flutter anew…

Ch4:

A sequel to Kemono ni Namida.