Arashi, Natsu and Semimaru decide it is time to return to Kyushu and rejoin their team using the sailing boat. Meanwhile, Takahiro, Haru and Hana find a tunnel entrance and two members of the Fall Team underground. One captures Haru who insists that he has been hearing the sound of a motor. When Takahiro's group go to find them, Akiwo and Ran and Team Fall take their inflatable raft and move further into the underground system which appears to be an evacuation complex. They find that power is available and they access the computer system. Meanwhile, Takahiro's group also explore another part of the complex where they find a body and a diary...