Toshinori's hero persona derives much from American superhero stereotypes, in which they are colorful and have a lot of dramatic flair. Always sporting a giant smile, he usually shows off a bright, can-do attitude that borders on being obnoxious. He also tends to be extremely friendly and amicable, due to his popularity and years in the spotlight. However, when he reverts to being sick and scrawny (as a result of a previous battle), he tends to be less energetic, both due to having no need to hide his worries about the state of affairs around him, and his constant blood-spitting. Additionally, he avoids drawing attention to himself altogether while in his true form, always afraid that others might learn of his current state of health.

Two personality traits always persist, though, whether he is in hero-mode or normal-mode: his optimism and his oafishness. He has always had faith and hope that someone would come along, worthy enough to bear One For All. Despite actually being more intelligent than his image would suggest, he is still sometimes depicted being outsmarted by his students, and even his fellow teacher, Shota Aizawa has called him an idiot a few times.

While he is seen smiling, laughing, and cheerful most of the time, he is extremely protective of his students, and is shown to be furious when he learned Villains were trying to get to him through his students. Even Izuku was surprised to see such a reaction. He was willing to use his Quirk beyond his time limit in order to save his students.

He possesses a fatherly attitude towards his students (Izuku in particular), which he often hides and keeps to himself. He is quick to give encouraging advice to them when the situation calls for it. He is proud of their accomplishments.