Issei Tachibana The eldest of the Tachibana quadruplets. A bright, energetic mood maker who loves jokes and pranks. He has outstanding reflexes and excels at acrobatics. He is caring and devoted to his siblings, leading them like a true eldest brother when it counts. When the siblings were separated as children, he chose to go to an orphanage himself to spare his younger brothers from hardship. He also has a scar on his back from protecting Itsuka. He is friendly and often teases Yua, but he treasures his little sister more than anyone.

Mitsuki Tachibana The third son of the Tachibana quadruplets. A second-year middle school student. He participates in shoots and entertainment activities as part of the 'Tachibana Brothers.' He has a blunt and somewhat aloof personality, but he is actually kind and cares for his family more than anyone. Once he opens up, he can get carried away with mischief. He loves music and is skilled at songwriting; he secretly posts music under the name 'luck.' He struggled with their mother's death and went through a period of school refusal. He shows a tsundere side toward people he likes. He generally refers to his brothers without honorifics. While he can be curt with Yua, he is actually very devoted to her and looks out for her in subtle ways.

Shiki Tachibana The fourth son of the Tachibana quadruplets. A second-year middle school student. He has a calm, prince-like personality and is gentle and kind. He is good at cooking and aims to be an actor. He also participates in shoots and entertainment activities as part of the 'Tachibana Brothers.' He has a somewhat frail constitution. Due to the shock of losing his mother, he lost his voice for a period of time. Usually mild-mannered, he shows a strong side in emergencies. He calls his brothers 'Big Brother [Name].' He is gentle with Yua and is always looking out for her.

Itsuka Tachibana The youngest of the Tachibana quadruplets. A second-year middle school student. Bright, honest, and a pampered 'healing' type. He loves soccer and has great athletic ability. He is friendly and looks up to his older brothers. After their mother died, he was taken in by relatives but was hurt by comments like 'the older brother would have been better.' He treasures memories of his father and started soccer because of his influence. He calls his brothers 'Ichi-nii,' 'Nii-ni,' 'Mitsu-nii,' and 'Shi-nii.' He is bright and affectionate with Yua, talking to her innocently. He also deeply cares for his sister.