Family#
Mahoro Shimano#
Katsuma loves his older sister deeply. After the premature death of his mother and because his father is usually absent due to work issues, Mahoro is in charge of watching over and taking care of Katsuma, which is why he appreciates her a lot and has a very close relationship with her. Both siblings help each other when one has problems.
The only thing they do not agree on is their opinions about heroes, since Katsuma admires them but Mahoro often disparages them, and he constantly tries to show his brother that they are not as great as he thinks, to the point that he forces him to participate in their shenanigans to prove it to him. The appreciation he feels for his sister, together with the fact that he is very shy and insecure, makes Katsuma not usually oppose her and obeys her in everything.[1]
Mr. Shimano#
Despite the fact that Mr. Shimano is usually absent due to work issues, Katsuma loves his father very much and always looks forward to his return home. The first thing he did after Mr. Shimano returned to Nabu after being attacked was run to meet him at the port and hug him.[1]
U.A. High School#
Izuku Midoriya#
Katsuma meets Deku while he was participating in the Hero Work Recommendation Project program on Nabu Island. The first times was during his sister's antics, and although she underestimated him for his poor performance in his hero's duties, Katsuma acknowledges that Izuku always comes to help them whenever he was requested, and even if it was a farce, he did not hold a grudge against them.
Because of this, Katsuma apologized to Deku for her sister's antics, starting a better relationship when they discover that the two share a similar admiration for heroes. Izuku realizes that Katsuma wants to be a hero, although Katsuma didn't considers his Quirk good for that. However Izuku assures him that anyone can be a hero as long as they focus on putting their effort, which makes Katsuma very happy.
During Nine's attack on Nabu Island, Katsuma's admiration for Izuku grew as he constantly protected him from the villain who wanted to steal his Quirk. He was flattered very time Izuku praises him for his bravery and thanks him for healing his wounds with his Quirk. After the attack, when Izuku leaves the island with his classmates, Katsuma runs to the port to say goodbye to him, promising that he will become a hero like him. Happy, Izuku replies that he will be waiting for him at the U.A.[1]
Katsuma would eventually follow up on Izuku's words and would begin attending U.A.'s Hero course eight years after the Final War.[2]
Katsuki Bakugo#
Unlike with Izuku, Katsuma's relationship with Katsuki did not start in the best way, since the latter reacted violently to the antics of his sister in which he participated, so Katsuma was initially afraid of him. However, during Nine and his gang's attack, Katsuki did his best to protect him and his sister, so she began to respect and admire him. Although their relationship is not as close as Izuku's, he also says goodbye to him when he leaves the island, promising him that he will be a hero.[1]
Mezo Shoji#
Although their interactions were not as frequent as with Izuku and Katsuki, Katsuma is very grateful to Mezo for constantly protecting him and his sister from Nine's attacks, to the point of acting as a human shield to save their lives.[1]