Year 20YX. Global warming is causing sea ice to decrease in the Arctic Ocean. The Maritime Self-Defense Force destroyer Shiranui, on which Kaburaki, a candidate to become the next captain of the Ibuki, is dispatched to conduct research. Suddenly, a civilian research vessel is attacked by someone. The Shiranui quickly uses its weapons to protect the civilian ship, but who is behind the attack?

(Source: MU)