Tsushima is an island nation made up of three distinct races of people. The Akitsu race is the dominant group, accounting for 80% of the population, while the Shiomi population comprises the top 10%. The remaining minority is made up of the Oina race, known for their distinctive tails and cat-like ears. Tsushima is renowned for its powerful military force.
Mikasa Sanekiyo, formerly of the Sakune clan, was adopted by another family after losing his parents and grandparents. His brother-in-law, Mitsukiyo, is an accomplished military commander, and Sanekiyo admires him as a moral and emotional role model. Sanekiyo follows in his footsteps and is appointed the top chair of his class at the navy academy. However, he is unaware of the Akitsu's strong prejudice towards the Oina and Shiomi races, and he finds the going tough during the grueling training period. To one day lead the navy fleet, Sanekiyo must learn to be a great leader and surmount these hurdles.