The Hitman Stans, Vol. 1 (manga)

Meet “the Killing Machine” Owaru Endou: the cold-blooded and strongest hitman of a massive underworld organization who has decided to retire out of the blue. His reason? To stan his favorite underground idol with his head held high! But old habits die hard, especially for a man whose hands are stained with blood. Can Owaru truly shed his identity to live the ultimate fan life of concerts, meet and greets, and picture lotteries—even when his past comes knocking?