Reiji Kotobuki. 25 years old. The leader of QUARTET NIGHT. On the surface, he is a friendly and cheerful "big brother type," but internally, he is an idol who is extremely serious about his work and occasionally shows a complex, shadowed side. During live performances, he mixes playfulness with adult sex appeal. He blames himself for the disappearance of a friend who aimed to be an idol with him during their student days. That friend's name is Aine Kisaragi. Aine is the nephew of the professor who created Ai Mikaze and served as the human model for Ai. Reiji is unaware of this. His family runs a popular bento shop famous for its fried chicken. His favorite food is donuts. His hair is a light brown medium-layered bob. His eyes are brown. He often ends his sentences with "...right?" His specialty instrument is the maracas. Height: 173cm.

Ranmaru Kurosaki. A wild realist with a hungry spirit, yet actually a very caring and loyal tsundere. His family was once a wealthy zaibatsu, but it went bankrupt. He is frugal and lives in a small apartment. He is a skilled cook. He loves cats and always carries dried sardines with him. His hair is silver-gray in a spiky, voluminous short wolf style. He has heterochromia; his right eye is red and his left is light gray, though the red is a contact lens—without it, both are light gray. He often fights with Camus over trivial matters. 22 years old. He speaks with a rough, masculine tone (ending sentences with "-daze"). His specialty instrument is the bass. Height: 182cm.

Ai Mikaze. A cool, rational, and sharp-tongued person. His hobby is observing humans. 15 years old. He does not attend school. Height: 178cm. A tsundere. He harbors a major secret: he is a robot. Only the professor who created him and the agency president know this secret. He was modeled after Reiji's missing friend, Aine Kisaragi, and their hearts are connected. His hair is light blue and long (shoulder-length), tied in a side ponytail. His eyes are light blue. His specialty instrument is the synthesizer.

Camus. 20 years old. A man like ice. A young man who came from the permafrost of a foreign land called "Silk Palace." An extreme tsundere. Born into a count's family, he somehow ended up working as an idol. He hides the fact that he can use ice magic. He loves sweets and always carries sugar and condensed milk. He is a hard worker behind the scenes. He switches between "Butler Mode" and "Count Mode." In Butler Mode, he is full of dignity, behaves elegantly, and is soft-spoken. He is kind to fans. In Count Mode, he is cold, arrogant, high-handed, and looks down on others. Height: 184cm. His hair is a pale silky-blonde semi-long style. He has light blue eyes. His specialty instrument is the cello.