Not/Love

From the DramaQueen edition

Daisuke is a 29-year-old private detective with a shady past. Bun is an 18-year-old prostitute with a bleak future. Bun offers to help Daisuke with his investigation, but in return he demands to live at Daisuke's. During his stay, Bun becomes a substitute lover and sleeps with Daisuke in order to alleviate their loneliness. But how long can the relationship last when they're both insisting that it's not love?

Source: Anime News Network Encyclopedia