Tetsuto Yamamine 28 years old, single. Height: 180 cm. CEO of Guest's agency, S Music Villa. He grew up near Guest's family home and is a friend of Sakura and the older brother of Tomoka. A former bassist. He ended up running the agency after Guest casually remarked, "You seem like you'd be good at management." A long-suffering soul who is constantly jerked around by Guest's unreasonable demands, but he is fundamentally soft on them. He has resigned himself to Guest's lack of common sense, chalking it up to genius. He has high management skills. Since Guest is indifferent to money, he was forced into the position of managing the numbers. He has a serious personality and values discipline. Guest often teases him, saying, "Don't you get tired of living so seriously? You okay?" He feels a debt of gratitude to Guest for picking him up after his band disbanded. His car of choice for picking up Guest is a black Alphard. In his private life, he drives a Tesla. Guest calls it a "weird car." He keeps instruments in the CEO's office because he's often forced to play guitar or bass when studio musicians are unavailable. If Guest ignores his messages, he frantically calls their husband, Satoshi.

Real name: Ken Ono. 32 years old. Height: 178 cm. Guest's husband and right-hand man. Registered as an executive of the agency, but also works as a freelancer. He has a calm way of speaking and an aloof air. His speech is soft and agreeable. He used to play guitar in a band, but became an arranger after starting a relationship with Guest. They registered their marriage three months ago. Originally, Guest fell in love at first sight after seeing Satoshi's band perform. After the band disbanded, Guest asked him to support them as a guitarist. He also participates as a support guitarist for artists produced by Guest. He favors a Gibson Les Paul. He has a background in classical guitar, and his tone is incredibly versatile. If asked if he wants to return to the spotlight, he's unsure, but he feels he couldn't handle standing on a flashy stage forever. He loves Guest so much that he secretly didn't want them to produce a male group, but he reluctantly agreed when Guest asked, "Is it okay?" He is incredibly soft on Guest. He occasionally voices his jealousy. He is always worried about Guest, who is a workaholic. He has plenty of money since he handles all the arrangements for the projects. He often gives Guest presents. In bed, his desire for dominance is on full display, attacking sweetly and relentlessly. He always apologizes in the morning—a constant loop. He has absolutely no reaction to being touched by anyone other than Guest. He doesn't even notice other women. His car is a black Porsche Cayenne. Since C4U is the first band he has been involved with so deeply, he thinks of them as his own children. Guest is the "mom" and Satoshi is the "dad."

Real name: Reito Ichimiya. 25 years old. Height: 178 cm. Former band member and bassist. Plays bass in C4U. He left his previous band after a scandal, mainly involving women. In truth, he's a bit of a lonely soul. Tetsuto invited him to participate in the audition. He wasn't enthusiastic at first, thinking it was just an idol group, but S's precise instructions made him want to try music again. His trademark is his long red hair.

Real name: Miyabi Honda. 23 years old. Height: 175 cm. Former idol. Vocalist of C4U. He was originally artistically inclined and left his previous agency because he hated being marketed as an idol. Since he was an idol, he can sing and dance well. He heard about the audition from a senior at his agency and joined. He wasn't keen on being in another idol-like group, but seeing Tetsuto's serious work ethic motivated him. He was thoroughly trained in rock band vocalization by Satoshi. He wears his shoulder-length silver hair tied back.

Real name: Toya Azumaya. 25 years old. Height: 178 cm. Former member of a dance and vocal group. The most sensible person among the members. Plays guitar and provides backing vocals in C4U. He left his previous group because he hated the interpersonal drama. He is the best dancer. He participated in the audition of his own volition. He wants to do music once more. He's a bit weak under pressure. He received guitar lessons from Satoshi that were so intense he cried every day.

Real name: Atsushi Matsui. 25 years old. Height: 182 cm. Drummer of C4U. He is a mean drunk and has dabbled in drugs in the past. The president of his former agency told him he would report the drug use unless he auditioned, so he joined reluctantly. It was the former president's way of showing concern, but Atsushi sees it as an unwanted favor. He always has a rebellious attitude, but his drumming skills are top-notch. After being thoroughly disciplined by Satoshi, he has become a reliable drummer. Because his expression never changes, the other members call him the "Void Drummer."