Haiga, a friendly and sociable freshman from the countryside, arrives in the city for college and quickly adapts to university life. During a campus tour, he becomes captivated by Kanae, a cool, beautiful, and incredibly talented upperclassman guitarist. Hoping to get closer to him, Haiga joins the same music club, the Multiphonics Research Club, but struggles to find an opportunity to actually speak with him.

One night, after a drinking party, Haiga accepts a dare from friends to visit a box spa, a discreet establishment in Shinjuku Ni-Chome that offers intimate same-sex services. Haiga, who has been questioning his own bisexuality, sees this as a chance to get a definitive answer about his desires. To his shock, the worker who greets him is none other than his aloof crush, Kanae.

Despite his initial nerves and confusion, Haiga lets Kanae take the lead. What was meant to be a one-time experiment becomes an obsession. Haiga finds himself unable to stop thinking about Kanae and begins spending all his money and picking up extra work shifts just to afford return visits. For Kanae, who keeps a clear separation between his job and personal life, Haiga is just another client at first. However, Haiga's earnest, innocent attraction and his desire to connect with Kanae outside of the transactional confines of the box spa slowly break down Kanae's professional walls.

Their relationship develops along two parallel tracks: Haiga as a paying customer during their scheduled appointments, and as fellow band members practicing and spending time together on campus. This creates a complicated dynamic where Haiga must determine if his feelings are genuine love or simply admiration, while Kanae struggles with his own insecurities and the difficulty of separating his growing affection for Haiga from the formulaic nature of his work as a sex worker. The pressures of Kanae's job and his fear that Haiga only desires him as a fantasy eventually come to a head, forcing both young men to confront what they truly want from each other.

The story resolves as they attend a music camp where their shared passion for performance allows them to connect on a deeper level. Ultimately, Kanae leaves his job at the box spa to pursue a real, committed relationship with Haiga, leading to a conclusion where the two live together happily. The complete narrative is told over two volumes and features a significant character arc where the cheerful and honest Haiga learns about his own sexuality, and the mysterious and experienced Kanae learns to accept genuine love outside of his professional persona.