Gabimaru reigns as the strongest and most ruthless assassin in his village. But now finds himself on death row—with only one way out: retrieve the Elixir of Life from a sinister island. Longing for freedom, he accepts the challenge. But with fellow convicts vying for the same prize and demonic beasts lurking, how will Gabimaru survive this harrowing quest?

In the story, the seasons have changed and it will soon be the second spring. Tatsuya and Miyuki have finished their first year at First Magic High School and are on their spring break. The two go to their villa on the Ogasawara Island archipelago. After only a small moment of peace a lone young woman named Kokoa appears before them. She has abandoned the Naval base and she tells Tatsuya her one wish.