From justpeachyicedtea :

“I love you.” “That’s disgusting.” The kouhai that confessed who was fidgety and red-faced, turned out to be Shuichirou. Although Atsushi rebuffs him in less than 3 seconds, this doesn’t leave him to his peaceful life, rather, it leads to a daily love attack from Shuichirou. Even saying his type is “girls with big boobs” doesn’t stop Shuichirou. In the midst of that, Atsushi tries to get Shuichirou to back off by doing perverted things to him…?!

Worried that his son might be gay, widowed salaryman Nobu asks his colleague for advice on the situation. Drinking his sorrows away, he meets the beautiful Hijiri and they end up spending the night together. Then next morning, due to circumstances, Hijiri ends up staying with Nobu.