Komachi Hikigaya is a member of her school's student council and the younger sister of Hachiman Hikigaya. Komachi is a middle school student of average height. She has medium-length black hair and, just like Hachiman Hikigaya, has a strand of hair standing straight from her head (Ahoge). In contrast with her older brother, her eyes are cheerful and expressive. She is usually seen wearing her middle school uniform. As of Season 3, Episode 12, she wears the girls' Sobu High School uniform. 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. Komachi often borrows from his old projects and asks him to help her study. She enjoys teasing her brother as she often tries to set up reasons to get him alone with Yui or Yukino Yukinoshita. She is sly in handling things like setting her brother up in a date like situations or tries to get things in her favor. Unknown to her, Hachiman is actually well aware of her tactics and tries to go around it as Komachi gets frustrated with him, thinking he is unaware or because of his lack interest in it. According to Hachiman, she's got the Big Three: cuteness, prettiness and good looks. Komachi is known for her charming personality which seems to attract everyone. Because of this, she mentioned to be a popular girl in her school despite the fact that Hachiman is her older brother (who was unpopular and not very well-known). Although mentioned to be popular she is only shown to hang out with Taishi Kawasaki. She is a kind and caring person with an easygoing personality. This can be seen when she requested help from the service club for Taishi and also in Chiba summer camp where she helped the elementary school students. She can also be serious and cold to people. In one incident, she refused to speak to her father for reasons unknown, which reduced her father to tears even to the point of him begging her to talk to him again. She also refused to talk to her brother Hachiman when he was rude to her when she tried to help him until he consulted her for advice and apologized. It is mentioned in the light novel that she often spends all weekend at home with her brother. Being aware of both the merits and demerits of being social and loner, she chooses the best options that favors her and also chooses when, where, how and to whom she must socialize.