Surprised to see the calm and collected Yuuya Koga crying, high school student Souta Tajima accidentally drops a bucket of water on him. Concerned, Tajima apologizes to Koga, who reveals he is crying over the death of his special goldfish—the one he got from the person he likes. He claims that a fat white cat with black patches killed his pet, which fits the description of Tajima's cat, though Tajima feigns ignorance.

Koga sees through Tajima's lie but sees it as an opportunity to reveal a shocking secret of his own. Tajima gradually becomes an irreplaceable figure in his life as Koga begins to rely on him for emotional support and the boys grow ever closer.