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?!

The fight between Gaku and Nagumo ends with Nagumo delivering a knockout blow. Down in the museum's basement, X confronts the JAA's chairman while X's gang takes on Shishiba and Shin on the upper floor! As these battles reach their climaxes, Sakamoto rushes to X--but can he make it there in time?