Retsujou Paradox: Banken wa Yoru, Kiba wo Muku

You've been holding in your carnal desires for so long, your body has become pitiful...

The next target of Seiji Kiriya, a private investigator, is Hiroki Yano, the go-getting secretary of a powerful politician who has "special information." To get the information he needs, Seiji succeeds in becoming Hiroki's "friend in bed." As they consummate their passion-filled physical relationship over and over again, Seiji realizes that Hiroki has feelings for a special someone and starts to get jealous. In comparison, Hiroki has a secret he can't tell Seiji, becoming overwhelmed with feelings for his new friend...

(Source: Renta!)