|“||My grades are pretty good even if I don't study. [...] That's because I'm a genius.||”|
–Yōko Katori about her abilities.
Katori is a girl with medium-length magenta hair with bangs, and green eyes.
Katori is a lazy and easily frustrated girl. She believes that where her talent takes her is the farthest extent that can be reached and any additional work is meaningless. After her squad lost against Nasu Squad, she became apathetic to regaining their position in Upper B-Rank, citing that if they lose then that is the way things are meant to be. When faced with criticism from her teammate Wakamura, she lashes out immediately and plays her superiority against him as a reason to why she doesn't need to work hard for the team.
Katori's frustration is most notably shown during the round 5 match where she easily fell prey to Osamu's spider tactics; her anger peaked when learning Osamu's reasons for pursuing the expedition, which she considered simple and heroic. After the match it is revealed that her frustration and laziness stems from her inability to properly work hard and study.
Despite her overly apparent negative qualities, it is shown that Katori can be quite formidable and quick thinking in combat. Katori is also shown to be a caring friend as seen through her relationship with Hana Somei. Somei is possibly the main reason why Katori joined Border in the first place as she saved her life during the first invasion.
Somei is Katori's childhood friend and next door neighbor. She would often come to Katori's house only to find her playing games. When Somei was prohibited from visiting Katori, Katori switched her bedroom with her brother, since his bedroom faced Somei's bedroom, and opened a window in the wall so they could talk, although she said she only wanted to organize her room. After learning that Somei saved her instead of her own parents, and learning from Somei that she planned to join Border, Katori decided to join with her. Somei is usually the peacemaker to Katori and Wakamura's fights, coldly scolding them at such moments.
Katori and Wakamura are often at odds due to their different views.
- (To Rokurō Wakamura) "What if, could if, should if, if we lose then that just means is simply not enough." 
- (To Rokurō Wakamura) "I don't want to be lectured by somebody whose gunner ranking is lower than my own. Upper Ranking's Limit is something that a person that has never achieved master tier will never understand." 
- (About her abilities) "My grades are pretty good even if I don't study. [...] That's because I'm a genius." 
- (About Osamu and Yūma) "Acting like you're the main characters of all of this... This pisses me off...!" 
- According to the BBF Opposite Sex Attraction Chart, Katori cares the most about looks in a relationship among all other introduced characters.
- She likes games, senbei crackers, friends, and winning.