Himiko is a very cheerful girl, to the point of smiling even after having presumably killed someone, displaying apparent sadistic tendencies.[5] This continues even when danger is imminent, as when Tomura Shigaraki was about to attack her,[6] but it tends to stop when she is bored or annoyed. Himiko is frequently seen blushing seemingly out of excitement rather than embarrassment, giving her a permanent look of what appears to be lovesickness on her face. However, she has shown that she can easily be embarrassed, such as when she thinks people are coming on to her,[7] or when she is naked when copying clothes of the people she has transformed into.[8]

Himiko is mentally unstable and has a very twisted perception of love. Despite wanting to kill the two girls, she attempted to befriend Ochaco Uraraka and Tsuyu Asui as they fought, affectionately calling the latter by her first name and describing the former as "lovely". When talking to Ochaco, she said that it was only natural to want to be like the one you love, to the point of literally becoming that person. While she declares liking guys who are tattered and reek of blood, being the reason she carves people up,[9]Himiko's interest isn't superficial, as her questioning Izuku Midoriya about his values implies.

Himiko is quite courageous, or at least very confident when using her Quirk, even impersonating an aspiring hero and taking part in an exam that gathered multiple students of heroics and pro heroes. She also has shown a comedic and childlike demeanor when faced with different situations, such as when she was with Twice or when she attempted to insult Mimic.

Like most of her allies, Himiko has stated that she finds life to be difficult for the current world and wants to make it an easier place to live in. She looks up to Stain and sees him as her role model; declaring a desire to kill and "become" him.[6] In stark contrast to her maniacal nature, Himiko has shown a very supportive side as she comforted Twice, knowing he feels the most responsible for causing Magne's death and covering a part of his ripped mask to prevent him from splitting.