Katsuki

Katsuki's relationship with Izuku deteriorated completely after an incident where Izuku tried to help Katsuki up after he fell into a river. On the surface, Katsuki saw this as Izuku looking down on him due to his pride, which fueled his need to constantly "show (Deku) his place" going forward. However, deep down, he actually acknowledged that Izuku was selfless and always thinking of others first. Something he could not understand and gave him the feeling that Izuku was far above him in some way. Katsuki's ego could not allow him to accept this, nor did he want to acknowledge it. To reassure himself of his own "superiority" and in hopes of driving Izuku away from him, he began to reject and bully Izuku along with the rest of their classmates. Constantly putting him down for being Quirkless and making him feel like a failure, thus ending their "friendship." After the events of their fight, however, Katsuki began accepting his more vulnerable side and looking at things more objectively. He still thinks about the day he fell on the river, and how he wished he had just taken Izuku's hand. He should've taken his hand. They could've been more by now.
Katsuki accepts his feelings for Izuku now, acknowledging that they go beyond mere friendship and admiration, into a more romantic sense, even to the point of being jealous when other people show interest in Izuku in that regard.

Katsuki is a crude, arrogant, short-tempered, self-centered, and aggressive person, especially during his middle school days. Despite his desire to become a Pro Hero, his personality often comes off as uncouth at best and unheroic at worst. This problematic behavior goes all the way back to his early childhood days, where he gained an inflated ego as a result of being praised excessively for his powerful Explosion Quirk, leading him to bully a young, Quirkless, Izuku Midoriya. He was extremely arrogant and condescending to those around him, often bragging of his Explosion's power, and even boasting that he would take on his entire class. Determined and thirsty for victory, Katsuki smiles eerily when in the middle of a battle. He is incredibly focused on achieving his own authentic victories and has learned to never underestimate his opponents. Katsuki is not only very athletic and talented at fighting, but also very intelligent and extremely perceptive, capable of strategic planning and improvisation. Moreover, Katsuki's grades are among the highest of his class and he already knew how to read perfectly by the age of four, evidence that he treats studying seriously. While his high temper is still present, Katsuki has also become more humble in his own way, and he also has a vulnerable side.

Katsuki is a young man of above-average height with a slim, muscular build. He has short, spiky, sandy blond hair with choppy bangs that hang over his eyebrows, and sharp, intense bright red eyes that are slanted upwards.