Kuubo Ibuki: Great Game

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 attacked it? What was the reason for the attack!