The Mole Song: Undercover Agent Reiji 2013

Reiji Kikukawa, who has a strong sense of justice, graduated from the police academy with the lowest score ever. He becomes a police constable, but is suddenly fired by the Police Chief due to "disciplinary" issues. In actuality, the firing is part of a carefully orchestrated plan. Reiji is ordered to become a "mole," an undercover cop. His target is Shuho Todoroki, the boss of the Sukiyakai gang....