Aoi Minamo is hired to be Haru's assistant. When burning sea causes a power outage that threatens life support systems on the artificial island, Minamo rushes to the electrical substation, while Haru uses his cyberbrain to dive into the Metal Network.

Minamo searches for a pair of antique Sous-Marin sunglasses as a gift to congratulate Haru on becoming an official investigator. During the search, Minamo and Sota have a run-in with champion fighter Iron Schwartz.

Haru reminisces about his youth, from his parents' struggles with poverty that led to trouble with the yakuza, to his meeting a dolphin that inspired his fascination with the sea, and finally to his exploration of the ruins of his city, now underwater because of climate change, which led him to become a test diver for early Meta-Real experiments.

Kushima goes missing, and is later found without his cyberbrain. Brain death will occur within twelve hours, so Sota and Holon search for his cyberbrain while Haru searches the Metal for his consciousness. Meanwhile, with Kushima missing from the Trustee meeting, the Secretary-General has no choice but to approve Jeni En's motion to begin bringing the weather particle plants online.

Haru makes contact with Eliza and receives Kushima's proof that the weather particles will cause worldwide disaster. Haru broadcasts the proof on the Metal, and the world's leaders quickly agree to shut down the Metal to kill the weather particle nanomachines. Kushima's consciousness then contacts Haru and explains that the ocean itself will replace the functionality of Metal via the salt water in the human body. Haru, restored to his younger self, is safely returned to the surface, where he reunites with Minamo.