Kondo, Okita, and Saito have finally found and retrieved Seimei from the bandits. Peacefully sleeping in his coffin, Seimei is loaded onto an airship for transport back to Kyoto, but the ship catches fire and crashes. When the three men come to, they find themselves on Prison Gate Island, a man-made island in the middle of Lake Biwa where criminals and rebels are kept. On the island they encounter a mysterious man calling himself "Black Snake" who saves them from the other criminals trying to hunt them. The mysterious man turns out to be Takasugi Shinsaku in disguise, since he had been unceremoniously deposited on the island by Mugensai. Will the four men be able to cast aside their differences to retrieve Seimei and make it off the island?