Shura suddenly goes missing. However, based on her last traces, Mephisto deduces the high possibility that Shura has returned to her hometown in Aomori Prefecture. As such, he orders Rin and Yukio to go there and search for her. After investigating, the twins arrive at Lake Towada in Aomori. Shura was facing off against Hachirotaro Okami, a powerful Hydra who claimed the large territory centered at the lake and the surrounding areas. Hachiro and his snake companions urge Shura to fulfill her promise to him.

With Yukio's clever wit, Rin and his friends are able to deceive Hachiro and successfully get him to break his contract with Shura. However, Hachiro loses all control in a rage, capturing Shura once more and heading toward the frozen lake. When the immortal Hachiro expresses his wish to die, Shura tells him they will sleep together forever at the bottom of the lake and embraces him. But as they sink into the lake, memories of the days she once spent with Shiro flash through Shura's mind.