Hiro is a high school student with a strong passion for adventure. Legend has it that something truly wonderful is hidden around his hometown, but the only problems are figuring out what it is and where to find it. After discovering a book filled with strange text in the college library, he recruits his friend Puri to translate it for him. She determines that there is indeed a legend involving a hero and his companions, who team up to find a magical cave. Meanwhile, a young woman named Fauna is afflicted with a very unusual condition that causes her to yearn for sex uncontrollably while she sleepwalks. Due to the possible dangers this puts her in, she and her friends are concerned enough to entertain the possibility of a local superstition. Allegedly, there is a flower that can help cure any ailment, and if true, it could be the solution to Fauna's problems. Neither of the parties in Rhythm: Koi no Rhythm realize that their separate paths are one and the same, and their intersection will lead them on an adventure none of them will ever forget.