|“||That's gonna be easy! I'm a genius, after all!||”|
Katori is a light-skinned teenager of average height and build. She has green eyes and straight, medium-length magenta hair with a middle-parted bang, black highlights and tips that curl sideways at the height of her shoulders. When she was younger she often wore hoodies, whereas after the match against Tamakoma Second she could be seen wearing a dark checkered shirt with bracelet sleeves and white trousers.
Her uniform consists in a tight-fitting bodysuit that reaches halfway through her calves, with short sleeves and a high, rigid neck. The suit is mostly black, with a color scheme that makes it look as though Katori were wearing on top of it a purple jacket with white lining and short straps on her hips. Three red vertical lines starting at the top of her collar and reaching down to her waist, each tapering off into a point, and six silver ornamental buttons, arranged in two columns of three on her chest, decorate the bodysuit. Two similar buttons can be found on each of her short sleeves, two more on her back, and a final pair on her hips. The uniform is completed by shoulder-length purple gloves with a black dot on each knuckle except for the thumb, identically colored calf-length boots with black soles, and one black holster with a purple horizontal line on each hip. The speakers of her communication system, black in color and shaped like a comma with a triangular hole at the center, can be seen through her hair.
Liberally calling herself a genius, Katori can easily come across as arrogant, lazy, and extremely self-satisfied with her talent, which allows her to achieve stellar results at anything she tries her hand at with very little effort. However, her enlistment in Border has caused in her a crisis of confidence, which first manifested in her repeatedly changing her class. Though she claimed to have grown bored with each class she switched out of, in reality she perceived an insurmountable wall separating Border's strongest agents from her, which discouraged her from devoting time and energy to honing her skills: if before she never felt the need to work hard to improve herself, her experiences competing against Border's top agents taught her that there was no reason to do so in the first place, as matching them would be impossible, despite having never made an effort. She began to believe that where her talent takes her is the farthest extent that can be reached and any additional effort is meaningless.
After dropping to the mid-tier of B-rank and losing to Nasu Unit her frustration caused her to appear apathetic about her unit's ranking, whereas the defeats deeply demoralized her and filled her with self-loathing, which further fueled her self-defeatist attitude. She developed a tendency to lash out harshly when criticized, playing her superiority against the interlocutor to disqualify their opinion, and responded curtly to statements about how motivation and resolve can help achieve one's goals. She took the defeat at Tamakoma Second's hands especially hard, so much so that she considered quitting Border altogether, which Yūta Miura understood to be because she actually envied their opponents' ability to work hard towards their goals. It is only then that she discloses her displeasure with being unable to apply herself.
Katori's personality reflects on her performance in rank battles. Recent disappointments caused her to lose interest in strategizing and gathering data on her opponents. Against Tamakoma Second her belief in her allegedly superior skills caused her to act recklessly, charging at Yūma Kuga on her own against her teammates' advice. Nonetheless, she later proved capable of maintaining a cool head while fighting, as well as to use the impression that she had gone berserk to her own advantage. To distract Osamu Mikumo she did not shy away from employing psychological tactics in which her own disappointments seeped in.
Somei is Katori's childhood friend and next-door neighbor. She would often come to Katori's house, she studying and Katori playing videogames. When Somei was prohibited from visiting Katori, Katori switched her bedroom with her brother, since his bedroom faced Somei's, and opened a window in the wall so that they could talk. Katori tried to play it cool by pretending that she just wanted to rearrange her room, to no avail. After learning that Somei saved her instead of her own parents, and that her friend planned to enlist in Border, Katori decided to join with her, convinced that with her talent they would be able to achieve anything. Despite Somei studying much harder than Katori when they were younger, she was not bothered by her friend boasting about achieving superior grades with little effort, although she does warn her that she plans on climbing to the top of Border. On occasion Somei does chide Katori for not taking her duty seriously enough, but unlike Wakamura she never seems to prod her to improve, presumably because she knows that at the end of the day Katori will do what she wants. To this day she remains unfazed by her temper tantrums, her bluntness occasionally frustrating her. However, she encouraged her when she feared that she would not be able to improve, sensing that Katori was finally willing to make an effort. Somei is one of the few people who can make an emotional Katori listen to reason, whether it be while fighting or when she argues with Wakamura. However, she does not intervene in the arguments unless they directly affect the performance of the team. Katori and Somei are on a first-name basis, neither using honorifics.
The demotion to the mid-tier of B-rank has exacerbated Katori and Wakamura's relationship. He is very outspoken in his criticism of her, sometimes excessively so, taking a harsh tone which causes her to respond back in kind. His calling her out on her detrimental lack of motivation before the match against Tamakoma Second sparked their harshest argument yet, with Wakamura pointing out that she would need to work hard before she can complain about there being nothing she can do, and Katori responding to his criticism first by mocking his skills, then by throwing her phone at him. On that occasion Wakamura seemed to acknowledge that part of his frustration with her is due to his own insecurities and envy. It is only after the fight that Wakamura realizes that Katori would actually like to work harder, but is afraid of being unable to do so. The two are on a first-name basis. Neither appends an honorific.
Miura has had an unrequited crush on Katori since he first met her, which may cause him to lose all willpower when speaking to her. He attempts to pacify Wakamura and her whenever they fight, although never with success. Despite rarely speaking his mind, he appears to know Katori very well, being the one who suggested that she might be feeling envious of Tamakoma Second. He addresses her by her first name followed by the diminutive suffix -chan.
Katori's mother is aware of her daughter's intellect as well as personality flaws, calling her out on her arrogance, laziness, and attempts to look cool in front of Somei, although always in a very gentle, light-hearted way.
Katori is exasperated by her father's very public displays of affection for her and the openness with which he talks about feelings in general, especially her own. For his part he is unaffected by her rebuffing his affections and her occasional acting spoiled.
Katori's brother did not hesitate to trade rooms with her to let her be closer to Somei when the latter was forbidden from visiting. Like the rest of their family, he can easily ignore Katori's tantrums and enjoys teasing her when she tries to put up a stoic façade.
Katori has a very blatant crush on Karasuma.
Over the course of their match Katori grew to despise Tamakoma Second, and in particular Osamu and Yūma. Osamu's response to her attempts to distract him - that he was simply doing what he believed he had to do - infuriated her, presumably due to her struggle with motivation and her own recent defeats. Her rage intensified when she grew convinced that Yūma and he behaved as if they were the main characters in a story. In reality, however, her hostility is due to a profound envy for the successful, hard-working newcomers.
- (On various occasions) "It pisses me off."
- (To Rokurō Wakamura) "What do you mean we can't afford that? If we lose, that just shows we're not capable, right?"
- (To Wakamura) "I don't want to be lectured by somebody whose Gunner rank is below mine."
- (To Wakamura) "There's a wall that separates the elite from the rest. It must be hard for someone who's never become Master Class in anything to understand."
- (To Wakamura) "What're you so heated up for? So lame..."
- (To her teammates) "You guys don't have a problem with this, right? As long as I win..."
- (To Wakamura) "Don't blame me! You're making me not want to do this!"
- (To Wakamura) "You protect me because you won't be able to win without me, right? Can you stop being so condescending?"
- (To Osamu Mikumo) "Do you seriously believe in stuff like... 'It's to protect those who are precious to me' or... 'If I try my best, my dream will come true'?"
- (To her mother) "I don't need to study. I always get good grades. PE, music, art, whatever - I always do better than Hana. I'm a genius, you know."
- (To Hana Somei) "It's nothing to do with your family business. I'm doing this cuz I wanted to rearrange my room."
- (To Somei) "If we team up, we'll be unstoppable!"
- (To Somei) "That's gonna be easy! I'm a genius, after all!"
- "These guys are acting like freaking heroes!"
- (To her teammates) "I'm done. I'm so done with Border. The more I lose, the more I hate myself. So I'm quitting!"
- (To her teammates) "I really suck at studying or being creative..."
- Katori likes video games, senbei (Japanese rice crackers), friends, and winning.
- Her chest becomes more voluminous when she is in her trion body.
- Kazuaki Ōji's nickname for Katori, "Katorine" (カトリーヌ Katorīnu?), is possibly a play on words based on the English name "Katherine" and its variants.
- The foreign origin of her nickname creates a motif that she shares with Miura and Wakamura.
- Katori is very concerned about popularity (being the second Border member to care the most about it after Takeru Yuiga), to the point of ripping off the designs of Kirie Konami's and Nasu Unit's uniforms to increase hers. Her efforts paid off, since she does have admirers.
- Katori cares the most about looks in a relationship among all Border members introduced prior to the publication of the databook.