Hijikata and Sougo from the Shinsengumi find themselves chained to each other in a strange place. After they remember how they got there, a mysterious man shows up in a TV. The man tells them that if they can't get the key, which unlocks their chains, in 72 hours the bomb which is located in the Shinsengumi headquarters will explode. He also says that if one of the two gets the key and frees oneself from the chain around their neck, the chain of the other one will explode.