Ryo was hired by a doctor dying of cancer, who was willing to pay with her life-insurance for him to slay the sadistic boxer who murdered her lover. Upon completing the task, rather than taking her life-insurance and letting her go back to drowning in alcohol, Ryo did THIS instead. Cue Manly Tears from audience.
The anime only "Farewell, hard-boiled city" two part episode. After Ryo fool around a bit too much for Kaori's tastes, she furiously leaves the agency and disappear. She's later revealed to have been brainwashed into Sarah, a world wide terrorist with multiple indentities ( She's a different woman each time. ) Sarah threatens to blow up Tokyo with a nuke. Ryo goes to the rescue but doesn't try to fight when he recognize Kaori. The brainwashed Kaori shoots Ryo in the shoulder and begs him to stop coming closer. Ryo shoots and disarms Kaori still under brainwashing and as Ryo try to figure out how to disarm the bomb, he's unable to move and has only one bullet left. Before trying to cut a wire ( Which he has no idea which is the good one. ) with his last bullet he confess to Kaori and kiss her.