Naoya Inaba (Nakajima Yuto) grew up abroad and from his childhood experience, he thought “yankees” were the strongest heroes (in Japan "yankee" refers to delinquent youths). He was influenced by Japanese yankee manga while abroad and because of his own experiences and mangas, he is always full of chivalrous spirit.

Naoya arrives to spend a year in a high school in Japan. He attends a technical high school which emphasis on the location being center of "water polo supremacy" but is on the verge of closing down. Naoya admires the school because a yankee, whom he admired as a child was once a student there. However, he soon realizes that there are no real yankees like hero figures, only students who spends their days meaninglessly. Naoya is disappointed and decides to do something about it.