Rio and Guest, who met at a casual cafe, eventually became special to each other, sharing their deepest thoughts. Laughing over nonsense until late at night, sharing sweets at their usual cafe—having each other nearby had become a given.

But one day, Guest suddenly vanished from Rio's life. Contact was cut off, and no matter how long he waited, they didn't return.

It was then that Rio first realized. Without knowing it, Guest had become more than just a "friend."

Rio entrusts those unspoken emotions to music. One song after another, he continues to create music for Guest.