Mitsuki was revealed in the fifteenth arc of the series, the Monster Association arc, characterized by a series of sensational events and character growth. This character would definitely be a sight to see during season three of One-Punch Man due to the change of narrative she would bring to the anime's world.
Mizuki, alternatively referred to by her hero name, Captain Mizuki, is a B-class hero ranked number 71 in the Hero Association. She is a uniquely designed character created by Yusuke Murata. First off, Captain Mizuki dispatches the long-retained stereotype regarding female superheroes, in which they have model-like or slim figures that sometimes don't match their abilities. Captain Mizuki is depicted as sturdy, muscular, and fit while portraying her femininity despite her imposing figure. One of the first instances where she was first revealed in One-Punch Man manga was Chapter 93, where she was portrayed as a model athlete that decides to become a superhero to save the city from a monster invasion.
Captain Mizuki's physical abilities are closely linked to her body strength, which raises her strength level well above that of an average human. Due to her constant exposure to sports, especially track and field-related events, Captain Mizuki's hero regalia is a sports bra and spandex shorts. She also wears three gold medals on her neck.
As a support team member in the Monster Association Arc, Captain Mizuki played a key role during the raid. Despite the somewhat gloomy job of being a professional hero in the series, Captain Mizuki retains her cheerful personality. Captain Mizuki reveres Superalloy Blackluster, the S-Class hero that outclasses most heroes in the series in terms of physical fitness. Mizuki uses the advice she receives from Superalloy Blackluster as motivation during her fight with Nyaan, a powerful member of the Monster Association. Her unyielding will was also revealed when she refused to surrender because of a task that was entrusted to her by Child Emperor, an S-Class hero.
Captain Mizuki's physical abilities are exceptional, and she uses them in a sporty manner while fighting. She defeated several Tiger and Wolf-level monsters, attesting to her strength as a B-Class hero. She can also hurl weighty weapons easily, which was highlighted on several occasions in the manga. Due to her exceptional physical abilities, Captain Mizuki's jumps exceed a certain number of meters; her reaction timing during fights and her running speeds are notable. Mizuki often uses a special baton that can change into different shapes as a weapon during fights. Since her fighting style is based on different sports, her baton becomes crucial as a javelin during clashes with monsters and villains.
In the Monster Association Arc, Captain Mizuki requests Sekingar to blow her whistle for her to perform excellently, showing the close connection between her abilities as a sportswoman and a hero. Captain Mizuki also uses her three medals as weapons while fighting. She uses them as a discus, which can be deadly. Additionally, she performs other sports-related forms, such as shot put, pole vault and even hammer throws during battles; a sportswoman to the core.
Despite Captain Mizuki's notable strength, currently, she can only comfortably defeat Tiger and Wolf-level monsters. This was clearly seen in the manga, where she soloed several monsters easily. When confronted with Demon-level or Disaster-level monsters, Mizuki becomes somewhat handicapped. This happened during her confrontation with Rhino Wrestler and Nyaan. Rhino Wrestler, a Demon-Class monster, withstood her attacks without budging.
Regardless, Captain Mizuki is a noteworthy hero, a force to be acknowledged and reckoned with. She leads a whole new perspective on the aspect of female characters in the anime franchise. Undoubtedly, One-Punch Man fans are eager to see what lies in the future for this unique character.