"I'm sure we'll get the target we're after." Shotaro, a ruthless killer, code name "S". But one day, the target is the leader of the "Waruiyogumi" gang's only daughter - Furukawa, 17 years old. The moment he points the muzzle at her, he feels something he never felt before! Shotaro feels his heart grow... A genius killer, now a young girl's bodyguard? The heartful killer comedy begins.