Onigase has a high sense of pride and morals and is extremely strict. She is displeased with the Student Council's flaunting of the school's uniform regulations, which begins the conflict between the Student Council and the Public Morals Committee. Though she is somewhat zealous and has a strong sense of justice, she does recognize the positive effect of the Student Council. Though she values the rules, she knows not to go overboard as she threatened to attack Myouri Unzen if he attacked Medaka Kurokami just because he didn't like her. Her motto is "Rule with an iron rod."
Onigase has light brown eyes and dark pink hair (originally brown in the manga) styled in two small ponytails. She wears a dark red, circular accessory with an x-shaped emblem on the back of her head. Onigase wears the standard uniform of a member of the Public Morals Committee. Ten years later, Onigase no longer sports her twin ponytails, and wears an outfit similar to her Enforcer uniform.
Student Council Executive Arc
Onigase is seen standing with Unzen, Fue Yobuko, Kanraku Kunisaki, and Rankaku Yoshinogari behind the other students at Medaka's inauguration ceremony. Onigase is first seen chastising Hisshuu Kanoya, Kenna Yatsushiro, Mahibi Moji, and members of the Kendo Club for their improper clothing, refusing to let them into the school building. Moji and his friends brush her off, much to her ire. Yatsushiro goes on to point out the Student Council, whose flagrant disregard for the school's dress code horrifies Onigase. She confronts the Student Council in their office, calling out all of the members on the problems with their uniforms. After Zenkichi Hitoyoshi, Kouki Akune, and Mogana Kikaijima have all had their uniforms corrected, Medaka asks Onigase to leave, citing that none of them had any bad intentions. Onigase initially complies, before quickly returning, furiously exclaiming that Medaka's embarrassing uniform is the worst of them all. When Medaka claims that she has never been embarrassed about her splendid body, Onigase retorts that she should at least be embarrassed by her uniform, and that exposing her breasts like that is indecent. The two continue to argue, until Medaka finally declares that she just doesn't want to change her clothing, much to Onigase's shock. After leaving the Student Council room, Onigase rages in the hallways, annoyed that Medaka has an approval rating of 98%, while the Public Morals Committee are generally disliked. Zenkichi calls out to her, promising to get Medaka to do something about her uniform, and asking Onigase to let the matter slide. When Onigase asks if he can really do anything, Zenkichi sheepishly admits he can't. He goes on to state Medaka has a small habit of exposing herself, which Onigase insists is exactly what she is trying to prevent. When Zenkichi points out Medaka's numerous accomplishments, Onigase asks him if he thinks she should let Medaka go just because she has been doing some good. She insists that when it comes to rules, everyone is on the same level, and that the Public Morals Committee must always stay neutral. She does admit that Medaka has fulfilled her duties as president though, a line of thought that leads her to decide to use the suggestion box to get Medaka to change her uniform.
Onigase later calls Medaka and Zenkichi to the outdoor pool, claiming to have received a request. An anonymous individual lost something in the pool, and wants it retrieved quickly before the water damages it. Onigase made up the request, thinking that while Medaka is in the pool looking for the object, she will modify her uniform to meet school regulations. Medaka jumps into pool with her clothes still on however, telling Onigase that even if it gets destroyed, it's just clothing. Medaka asks Onigase what she should be looking for, only for Onigase to jump in the water herself, answering: "My good conscience. And thanks to you, I've found it." After they get out of the water, Medaka reveals she has seven spare sets of uniforms, much to Onigase's surprise. As Onigase worries what she will wear to school tomorrow with no spare uniform of her own, Medaka tells her not to worry, as she won't abandon a person in need of help. The next day, Onigase is seen wearing one of Medaka's uniforms (which does not fit her at all), much to the amusement of the student body. A humiliated Onigase promises Medaka that she will get her for this.
Onigase runs into Hansode Shiranui and Zenkichi, and chastises Shiranui for eating in the halls. Shiranui swallows all of the food, much to Onigase's ire. When Onigase goes after Shiranui, Shiranui pushes Zenkichi on top of her, before giving the other girl a brief warning and running off. Onigase tries to give chase, only for Zenkichi to warn her that Shiranui is more untouchable than Medaka. Onigase ignores him, only to discover that they have been handcuffed together. When Zenkichi presses her for the key, she tries unsuccessfully to change the topic, before angrily admitting that she doesn't have one. After Zenkichi upsets her with the implications of their situation however, Onigase decides to lead him to the Public Morals Committee's office, where the key is kept. Questioned by Zenkichi, she admits that she is being targeted by the Mokkin Team, a pair of delinquents each wielding a baseball bat. The pair run into Medaka, who misinterprets their situation as the two of them working together to form a bond between the Student Council and the Public Morals Committee. Medaka handcuffs herself to Zenkichi, and then finds she cannot undo the lock, both Zenkichi and Onigase are notable displeased. As all three head to the Public Morals Committee's office, Medaka stops them several times to help other students. Onigase quickly gets annoyed with Medaka's multiple stops, prompting Zenkichi to point out how much different things are now that they are with Medaka. Onigase shamefully admits that since becoming an Enforcer, she has lost all of her friends. Zenkichi tries to comfort her, only to be angrily rebuked. When Medaka calls them out, the Mokkin Team reveals themselves. The pair attack Onigase, believing her movements sealed due to the handcuffs. Onigase tells Zenkichi and Medaka to get behind her, as it is her job to protect them. When Zenkichi and Medaka instantaneously defeat the Mokkin Team, Onigase is stunned. She then asks Medaka why the other girl couldn't just break the handcuffs, if she was capable of smashing a metal bat. Medaka then asks if it was okay to break them, prompting both Zenkichi and Onigase to slump in defeat.
Onigase is ordered by Yobuko to take a towel to Unzen at the music room. A somewhat flustered Onigase agrees. On her way, she runs into Medaka and Shiranui, much to chagrin. When the three arrive at the music room, they find the members of the Orchestra scattered about in a comatose heap, with a bloodied Unzen standing in the center of the carnage. Onigase is appalled at the damage, but still dutifully delivers the towel to Unzen. After hearing Unzen's explanation for his brutal tactics, Onigase thinks to herself that this is the policy of the Enforcers that she believes in, but this is going too far even for her. When Unzen attacks Medaka, Onigase is stunned, having been unable to see the strike at all. She expresses the same amazement at Unzen's second attack, noting that it was even faster than the first. Before Unzen can attack Medaka a third time, Onigase intervenes, refusing to allow even Unzen to attack a student who hasn't broken any rules.
When Unzen attacks Medaka as she tries to leave, Onigase manages to identify it is a thrown weapon, but still cannot figure out how Unzen is using it. When Unzen asks her if she has seen Shiranui breaking any rules, Onigase remembers that she saw Shiranui eating in the halls, but lies and says she didn't. After seeing Unzen destroy his phone, Onigase is stunned. After blowing a hole in the wall, Unzen admits that there probably was a problem with the soundproofing, to which Onigase timidly agrees. Before leaving, Unzen orders Onigase to pass on the message that all Enforcers are to leave the school immediately. After Medaka finishes her fight with Unzen, Onigase arrives at the Student Council office with Yobuko, both concerned for their leader. When Unzen questions what they are doing there, she asks how they could not come, seeing how things turned out. Though she asks after the Student Council, Unzen tells her to forget about them. When he tells the pair that they will have to work harder now that he is out of commission, Onigase immediately obeys.
Thirteen Party Arc
In the lunch room, Onigase and other Enforcer girls question Unzen about the Flask Plan. Unzen identifies Onigase and the others as Specials, then goes on to explain Abnormals and the dice test. When he states that the aim of the Flask Plan is create geniuses, Onigase is visibly perplexed. While Unzen describes his sister, Myouga Unzen, Onigase is seen looking worried. Onigase listens along with the other Enforcers as Unzen describes his sister.
As Zenkichi tells the Student Council they have to regroup outside the Flask Plan labs, Onigase arrives along with Unzen, Nekomi Nabeshima, Myouga, Shigusa Takachiho, and Kei Munakata to provide support. Onigase tells Zenkichi that the Loser Team came to help the Student Council. Onigase is insulted when Zenkichi labels her as the worst member of the Loser Team. She stands by the elevator with everyone else. As the Student Council head down the stairs, Onigase thinks it was a waste to come and save them. Together, the Loser Team prepares to fight the Plus Six. Onigase and the others are quickly captured by Yutori Chikuzen's hair; however, they are cut free by Munakata. While Yamami Tsurumisaki is preoccupied with Myouga, Onigase moves in low to attack him. She is chocked when her attack is blocked by Otome Yunomae, who allows Onigase's handcuffs to pierce through her body with no signs of discomfort. While Medaka and company prepare to descend to the thirteenth floor, Onigase and the others are still fighting the Plus Six. Onigase continues to fight Yunomae. Later, she, along with the rest of the Loser Team and the Plus Six, is defeated by Misogi Kumagawa.
Kumagawa Incident Arc
Following the defeat of both the Loser Team and the Plus Six at the hands of Misogi Kumagawa, Onigase is sent to the hospital along with the rest of Kumagawa's victims. Instead of external wounds, those who got pierced through with the giant screws took severe mental damage. At the end of the semester, Onigase is present for Medaka's speech. She is horrified by Kumagawa's new rules. On August twenty-second, Onigase is among Medaka's former enemies who show up to cheer for her during the President's Battle.
Kurokami Medaka's Successor Arc
Unknown Shiranui Arc
The Public Morals Committee are approached by Medaka asking about Shiranui; none of them remember her. As Zenkichi hovers near death, Onigase's voice is one of the many that gives him encouragement. She is also one of the people he remembers before preparing to fight Iihiko Shishime.
Bouquet Toss To The Future Arc
Weapons Specialist: As an Enforcer, Onigase is allowed to carry weapons while in school. She is known as "American Cuff Onigase" (手錠メリケンの鬼瀬, Tejō Meriken no Onigase) for her use of handcuffs (which she also uses as make-shift knuckle dusters) to apprehend students who have broken school rules.
Superhuman Strength: Despite her small size, Onigase is incredibly strong and nimble: she is capable of squeezing metal bars out of shape and cracking walls with her fists.
- Strangely, despite being identified as a Special by Unzen, Onigase is not a student of Classes 10, 11, or 12, but is instead in Class 3.
- Onigase's nickname, 手錠メリケ (Tejō Meriken), can be translated at either "American Cuffs" or "Cuff Knuckle". Both are fitting, as she special ordered the same type of handcuffs used by the American military and she uses them in a similar fashion to brass knuckles.