Unlike her brother Hachiman Hikigaya, Komachi has a cheerful, lively and somewhat airheaded and forgetful personality, which was shown when she revealed she ate the sweets her brother was meant to get from Yui Yuigahama and not telling him about it. Hachiman considers his sister to be an idiot and fool, at least when it comes to education, though she's indeed very intelligent and socially skilled. Komachi often borrows from his old projects and asks him to help her study.

