Taro Sakamoto was once a legendary hit man considered the greatest of all time. Bad guys feared him! Assassins revered him! But then one day he quit, got married, and had a baby. He's now living the quiet life as the owner of a neighborhood store, but how long can Sakamoto enjoy his days of retirement before his past catches up to him?!

Mafuyu attempts to complete his mission despite knowing he's a pawn for X. Meanwhile, Sakamoto and friends are running around the museum's exhibition hall, which has become a battlefield between the Order and X's gang. Who'll come out on top in this assassin battle royale?