Main characters ; : :A second-year high school girl who joins Silverman Gym to slim down. Unfortunately, due to a lack of regular exercise and her terrible eating habits, she tends to tire out easily and any progress she does achieve is quickly undone. However, as the series progresses, her condition slowly improves and she is revealed to have a hidden talent for combat sports. She also has a brother who runs a restaurant where she sometimes helps out. ; : : A second-year high school girl who is the student council president at the same school Hibiki attends. She is popular due to being a beautiful girl who excels in sports and academics along with coming from a rich family. She has a muscle fetish and joins the Silverman Gym mostly to satisfy these desires, and often expresses her desire for Hibiki and others to become macho. Unlike Hibiki, she is in much better physical condition. Her character is a reference to the author's previous series,
Kengan Ashura, being the younger sister of one of the characters appearing in the series, Shion Soryuin. ; : : A second-year high school girl who is Hibiki's best friend. Ayaka is a buff who likes watching films with Hibiki. Both she and her sister are daughters of a famous former pro boxer who founded his own gym called the Glory Gym. Because her father taught both of them how to box since their younger days, she is in excellent physical condition and is a capable boxer who coaches for their gym. Her training is such that she can do shadow boxing perfectly and even perform the infamous "Dragon Flag", known for extreme difficulties. ; : :A member of Silverman Gym's
Moscow branch. After losing to Hibiki in
arm wrestling, she declares herself her rival and moves to Japan, even transferring to Hibiki's school and staying at her house without permission. While not into strength training, she practices
sambo and manages to stay fit that way. She tries to maintain an image of a typical
Russian stereotype, but is really just an . She was the first person to figure out Satomi's secret cosplaying life. Like Akemi, she is directly related to a character from
Kengan Ashura; namely, she is the niece of minor character Ivan Karaev. ; : :The history teacher at Koyo Women's Academy, which Hibiki and the other girls attend. She is secretly a famous cosplayer—alias Yuria Riko—and joins Silverman Gym to maintain her figure for her con-going. Like Hibiki, she develops a crush on Machio. So far, Gina is the only person to deduce Satomi's secret double life as a cosplayer, as she is a fan of Yuria. ; : :A trainer at the Silverman Gym who regularly coaches Hibiki and Akemi. Hibiki develops a crush on him at first sight, which becomes her primary motivation to join the gym. He is a dedicated, kindhearted and polite professional who always earnestly helps and supports Hibiki. Although belying his charming demeanor and handsome profile, Machio is deceptively muscular. While Machio looks no different than a regular young man with his clothes on, he has such a large and well-defined physique that once he flexes his muscles, he reveals a muscle mass so large he literally rips his clothes, which contrasts with his baby face. It is revealed that he was a classmate of Hibiki's brother and Ayaka's sister, and a disciple of Harnold Dogegenchonegger.
Supporting characters ; : :An American movie star whom Hibiki and Ayaka are huge fans of. He is also Machio's mentor. He is a parody of
Arnold Schwarzenegger. ; : :Ayaka's older sister. She works as a boxing coach at the Glory Gym. ; : :Hibiki and Ayaka's homeroom teacher. Like Satomi, she is also secretly a cosplayer. ; : :Akemi and Gina's homeroom teacher, who is in excellent physical condition for someone her age and dislikes being called old. Her character is a reference to the author's previous series,
Kengan Ashura, hailing from the Kure Clan, a notorious family of assassins, and being the mother of one of the characters, Kure Karura. ; : :A man who works as a director for a TV station. ; : :Harnold Dogegenchonegger's secretary. He is a parody of
Jason Statham. ==Media==