Kotone invites the girls to swim at her family mansion's pool, where they meet Kotone's little sister Shinobu, who seems determined to have Kotone return home. Shinobu challenges Shizuku to a swimming contest to decide who Kotone should stay with, which Shizuku ends up winning thanks to some meddling by the family maid. Later, Yuu decides she wants her own scarf, only to find the one she had her eye on had been bought by Shizuku, so Haruka goes shopping with her. They find the scarf Yuu wanted, only for her to choose a different one instead.
文化祭の打ち上げでコトネ宅の温水プールに来た春香たち。プールの中でこっそりキスをしたり、みんなで泳ぎの特訓をしたりと、 いつも通り仲良くプールを楽しむが、そこにコトネの妹シノブが現れる。シノブはコトネに家へ戻るようにと説得を始め、さらにはしずくも初めて聞くコトネの秘密を口に出す。 それを聞いて激しく動揺するしずくだったが、コトネのためにシノブとの「勝ったほうの家にコトネが住む」勝負を受けることにする…。
학교축제의 뒷풀이로 코토네 집 수영장에 놀러오게 된 하루카 일행. 그러나 집에는 코토네와 시즈쿠의 사랑을 방해할 엄청난 장애물이 버티고 있었는데...
