Resuming from volume 1, Kataruma Kazumi ventures beyond the mysterious cave in order to find out who he really is, accompanied by Rin. The two come across a broken seal and Rin mysteriously vanishes without a trace, leaving Kataruma distraught. He then blacks out and finds himself in the forgotten legacy of the sea, where he meets a human named Isamu Uchiumi, a detective, who had come to find out what happened to his deceased older brother, Senzai. As the story progresses, Kataruma realizes that Isamu isn't so bad and the two of them work together to discover the truth of Aogashima island while faced with various challenges along the way.
18 parts