Yamato Keisuke, a promising freestyle swimmer, and Ninomiya Ami, a talented diver, are the children of two rival families who own confectionery shops. Two generations ago, Grandfather Ninomiya came up with an idea for an owl-shaped cake, but Grandfather Yamato quickly rose to the challenge and thought of a similar cake—except in Yamato's version, the owl had ears. Because they were priced the same, Yamato's extra ears were crucial, and that caused the Ninomiya confectionery business to suffer. Grandfather Ninomiya then fell ill from worrying about his shop. Before his death, his last words were "I was killed by the Yamatos," and since that moment the two families have been sworn rivals.