Gabimaru, a ninja member of a clan of assassins, is sentenced to death. He claims to have nothing to tie him to life, yet no method of execution manages to end his life. His meeting with Sagiri Yamada Asaemon, who seems to be investigating him, will change everything.

Gabimaru, Sagiri, and the others arrive on Shinsenkyo, and their battle for survival begins.

Gabimaru and Sagiri are in trouble during their first fight against the island's mysterious creatures. Gabimaru is unaware of these monstrosities and this puts him at a disadvantage in battle. The sudden arrival of Yuzuriha, the female ninja, will change the situation, but Gabimaru does not see clearly in her game.

Gabimaru and Sagiri's group cross paths with another Yamada Asaemon, Genji, who takes a dim view of Sagiri's involvement in the present matter. Meanwhile, Yamada Asaemon Tenza tries to find a way off the island along with his charge, Nurugai.