S1, E5: Hachiman's younger sister, Hikigaya Komachi, was asked to give advice to a fellow classmate, Kawasaki Taishi. Apparently his sister had been acting strange. His older sister, Kawasaki Saki (though Hachiman wasn't aware of this), was in the same class as Hachiman and Yui, so the Service Club decided to help with the issue. They come up with various ways to try to dissuade Saki from her suspici...