眉難市に夏到来！ 男乱海岸で眉難高校伝統の遠泳大会が開かれることになり、防衛部や生徒たちも活気づく。その中で、もっともこのイベントに打ち込んでいるのは生徒会長の百目鬼珠闘麗斗。地球征服もひとまず忘れ遠泳大会優勝に賭けるその情熱には、何やら雲仙新九郎との過去からつながる因縁があるようで……。そして激突する百目鬼と雲仙。勝利の鍵を握るのは……赤フン？
Summer has arrived in Mayunan City! Mayunan High School's traditional long-distance swimming competition is to be held at Otokoran Beach, and the Defense Club and other students are in high spirits. Among them, the one most devoted to the event is Student Council President Doumeki Tamato. His passion, which has him putting aside the conquest of the Earth for the time being and betting on winning the long-distance swimming competition, seems to be somehow connected to his past with Unzen Shinkurou... And so Doumeki and Unzen clash. The key to victory lies in... Red poop?
