Soushite Kimi ni Fureru Made

For a long time, Shuuhei Ibuki has been in love with Kaoru Tobita, the yakuza boss's son who picked him up. Ibuki stayed close to Kaoru, hiding his feelings. But one day, when he was masturbating while watching Kaoru's drunken sleeping face, Kaoru happened to wake up and hit Ibuki. Because of this incident, Ibuki decided to change their relationship, but Kaoru told Ibuki that he wanted to introduce a woman to him... "I only want Kaoru, I want to turn you into someone who belongs to me only." What was revealed later was a pure love mixed with obsession, possessiveness, and desire. (Source: Renta JP, translated and edited) Note: Chapter count includes two extras.