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?!

As Sakamoto and his friends hunt for the database at the JCC, Shin winds up in a serious duel with a teacher who might have information on what they want. Meanwhile, Sakamoto deals with Amane, a boy with a connection to X. Thanks to X's schemes, the JCC faces an unprecedented crisis!