When Tsukasa was a middle school student, she had a crush on transfer student Hayato and even confessed her feelings to him. She was turned down by Hayato. Now, Tsukasa and Hayato are classmates in high school. Hayato treats Tsukasa as just a friend, but Tsukasa still has feelings for him. Meanwhile, Hayato becomes attracted to Tsukasa. ~~ Adapted from the manga series "Mune ga Naru no wa Kimi no Sei" (胸が鳴るのは君のせい) by Konno Risa (紺野りさ).