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.