Masayoshi Kimura is a student in Class 3-E at Kunugigaoka Junior High School, assigned to the task of assassinating Koro-sensei before the end of the school year. He has short, spiky dark brownish-green hair and black eyes. His background is shaped by his parents, both police officers, who gave him the given name Justice, rendered in Japanese as Jasutisu. Deeply embarrassed by this unusual and flashy name, he asks everyone to call him Masayoshi instead. The constant teasing about his name caused his concentration to drop and his grades to suffer, which led to his placement in the lower-ranked Class 3-E. He was once a member of the track and field club and is recognized as the fastest runner in the class, making him one of the most physically capable students. His personality is generally quiet and shy, especially when his real name might come up, but he becomes active and positive when it comes to assassination attempts. He is serious, stoic, and rarely shows emotion, yet he is also strategic and intelligent, able to devise plans and think logically under pressure. His primary motivation is to claim the ten billion yen reward for killing Koro-sensei, but he also wants to prove himself and overcome the insecurities tied to his name. In the story, Kimura often takes on roles that require speed, such as finishing off targets after a sniper shot or acting as a fast-moving asset during group assassination exercises. He works closely with classmates like Ryunosuke Chiba and participates in mock assassinations with code names. His key relationships include his fellow Class 3-E students, with whom he collaborates and forms bonds over their shared goal, and his parents, whose choice of name he struggles with but eventually learns to accept. Over time, Kimura develops self-confidence and grows more comfortable with himself, becoming a dependable member of the class. He also comes to respect Koro-sensei deeply, recognizing the teacher’s dedication and the value of the lessons learned. A notable ability is his exceptional running speed, which he uses both in assassination tactics and in physical training. He is prone to catching colds easily, a minor but recurring trait. Through his experiences, Kimura transforms from a self-conscious student into a more assured and effective contributor to the class’s mission.