Yasashiku Koroshite, Boku No Kokoro O. summary:

Although only 19 years old, using his good looks and his body as a weapon, Kanzaki Nao is a natural gigolo. Being stabbed after a breakup, he is saved by a refined and dangerous man who is a Yakuza -- Murou Ryouichi, boss of the Ichinose-group. Stopping Nao from leaving the city after his wounds have healed, Murou brings him to his apartment and offers him a deal in order to pay for Nao’s treatment.Even though Murou tells him that he’s “not interested in brats”, he’s contradicting his words when he starts kissing Nao like a lover. What will happen to Nao who swears by himself that he definitely won’t fall in love.....?