What the Guardian Serpent Heard.

Kotoko receives a request for help from a giant snake, who is the guardian spirit of Tsukuna Swamp. It appears that a murderer named Tanio Aoi disposed of a body in the snake's swamp, but there's something that's just not sitting right with the snake. After learning about Kuro's powers, Kotoko asks Kuro to accompany her on this journey, but Kuro declines for a certain reason...