Hozuki Castle is a prison run by the Hidden Grass, well known for being notoriously difficult to escape from. Boruto and Mitsuki are sent there to protect Kokuri, a former member of a brutal band of robbers known as the Mujina Gang who's now targeted by assassins after betraying and deserting the gang.

The mysterious organization known as the Kara is about to take one of their plans to the next stage that involves a crucial item called a “Vessel.” However, having his own ambitions, Victor secretly panics as he tries to keep his true objectives hidden from Jigen, leader of the Kara, and the other core members