The Unemonori Group sets up a fitness festival at school. Chise, Fumino and Otome are all debating who should pair up with Takumi for the three-legged race. Fumino is even angrier at Chise for her attempts to promote bloomers in the festival, attracting the male students. Fumino fights back by promoting spats, attracting the female students. Divided, Fumino, Chise, and the others decide the winning outfit by letting Takumi decide. While Takumi tries to understand Nozomi's depression, he gets heavily bombarded by persuasion and fights between Chise's bloomers and Fumino's spats. Meanwhile, a mysterious principal arrives at the Stray Cats.
間もなく行われる梅ノ森学園の体育祭。 ストレイキャッツでは誰でも参加ＯＫのフリークラス二人三脚で誰が巧とペアを組むのかと大騒ぎ。
それと時を同じくして、迷い猫同好会本格活動一発目となる希の「踊ってみた」動画がインターネットで大人気に。 さらには、千世が梅ノ森学園の体育祭を全世界に配信すると言いだし、いつものごとく文乃と対立。
この全く関係ないような事柄が複雑に絡まり合い、梅ノ森学園に「血のブルマ事件」が勃発する。
