Koroshiya no Oshi

The best hitman of the underworld, Owaru Endou, leads a dark and secretive life, constantly bathing in the blood of his targets. However, his life takes a brighter turn when he becomes a fan of Kaori "Kaorin" Minaboshi, an underground idol from Rosaceae whose concerts Owaru always attends.

Feeling that his hands and dirty money are too stained to support Kaorin, Owaru decides to retire from his profession to earn a "clean" income and make himself worthy of his beloved icon. Unfortunately for him, old habits die hard; to protect what he holds dear, Owaru must return to his roots once more.