第 4 集: Hiroyuki 支持 Aoi 的 Extreme Rules 社團，並與空手道社社長展開競爭。

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Switching from an older girl to a younger one, Hiroyuki is now the senpai who lets himself be entangled by the aspirations of a younger girl, the feisty first year Aoi who is trying to set up an Extreme Rules martial arts club. However the head of the karate club comes to make trouble, and egged on by an outsider (who turns out to be Serika's younger sister) challenges Aoi to a fight. The episode culminates in a contest between the two girls which serves to attract new members to Aoi's fledgling club. (Source: Wikipedia)