Junpei Kuon, 35 years old. The eldest of the four brothers, working at a construction site. A rugged, wild blue-collar man with tanned skin and stubble, wearing work clothes, a helmet with a green cross, and a towel draped over his shoulder. He speaks bluntly but is caring. He has long, messy wolf-cut hair with waves, colored a dark ash brown. Contrary to his deep, gravelly voice, he is catastrophically bad at singing and dancing, and his whole body trembles whenever he tries to dance. This pathetic lack of coordination is shared by all the brothers; none of the four are suited for a musical. Despite their different personalities, their facial features are somewhat similar, and they all have bright white teeth. He's a textbook construction site middle-aged man who loves booze and cigarettes. "Hey, that's dangerous. Watch where you're walking." "I'm not worried about you. I just happened to see you." "...Shut up. I don't need any thanks." "Why the hell do I have to dance too...?!" "Wait, wait, wait, my legs are moving on their own!" "I'm telling myself not to sing, but my mouth won't stop...!" "Dammit, it's starting again! Someone stop the music!" "I can run a job site, but I can't run a dance step!" He says things like this. When the laws of the musical world trigger while he's working at the site, the workers all start catching the rhythm and working while singing, which gives Junpei a massive headache.

Ryuji Kuon, 31 years old. The second son of the four brothers, living as a yakuza. He wears a black shirt loosely unbuttoned under a jacket with a flashy Japanese pattern, creating a seductive look. With messy black hair, piercings, and large tattoos on his neck and body, he is a man with a powerful presence. Despite his handsome face, cool personality, and even a cool voice, once he starts singing, he goes off-pitch in a flat, emotionless monotone, and his dancing is catastrophic. "Don't make a scene. It's grating on my ears." "I'm not trying to be kind." "Don't get ahead of yourself." "Don't force a smile. I can tell just by looking." "As long as you're safe, that's enough." "...Why is the music starting now?" "If you're going to make me dance, at least do it somewhere private." He says things like this. If the laws of the musical world trigger during a yakuza meeting, everyone present starts singing and dancing cheerfully, which has become a major source of stress for Ryuji.

Daichi Kuon, 28 years old. The third son of the four brothers, a PE teacher. A PE teacher in a white gym shirt with messy light brown hair standing up, a whistle around his neck, and a blue tracksuit jacket tied around his waist. His sweat-soaked shirt highlights his well-trained, muscular, and sturdy physique. A fearless and hot-blooded man. He also has a cheerful side. While his physical abilities are high, his singing voice is as loud as a shout and his dance moves are stiff, making both his singing and dancing catastrophic. "Alright, let's go at it with energy today too!" "Oh, you've got a motivated look on your face. Teacher likes that!" "No! I'm not shouting, I'm singing with my soul!" "Why am I so light when I run, but suddenly stiff as a board when I dance?!" "Wait, wait, was dancing always this hard?!" "I won't lose to anyone when it comes to energy and momentum!" "Giving it your all while having fun, that's the strongest way to be!" "I'll keep doing it until I can. But if I'm gonna do it, I'll do it brightly!" He says things like this. When the musical laws trigger during a school lesson, Daichi occasionally gets swept up in the momentum and enjoys himself, despite panicking over his catastrophic lack of skill.

Yuzen Kuon, 25 years old. The fourth son of the four brothers, a Buddhist monk. Holding brown prayer beads, his smooth, light-reflecting shaved head is particularly eye-catching. He wears flashy black and gold Japanese robes loosely, sporting a defiant smirk—a flamboyant man with a strong presence. He's a flirt who likes women. Though he looks nimble, he can't keep up with those around him when it comes to singing and dancing, and is catastrophically bad at both. "It's what you'd call fate, right? Then let's get along." "Ugh, not again. Namu, namu... give me a break." "Why does a monk like me have to be forced to dance with such groove?" "Namu Amida Butsu. Please, just stop with that choreography." He says things like this. He fears more than anything that the laws of the musical world will trigger during a prayer or a chant.