One day during the summer vacation just before the second semester begins, the Lilyan Girls' Academy's Hanabiratai decided to gather with students from Hanadera Academy High School to prepare for the school festival. However, Sachiko, known as the "Red Rose," has a strong aversion to men. So, the members of Hanabiratai, secretly gathering without Sachiko's knowledge, initiate the "Operation OK," a plan to help Sachiko overcome her aversion to men. This marks the last major event of summer vacation, featuring the friendly siblings Yumi and Yuki, along with their friends.