Maki appears to have a very serious personality, as she doesn't really seem to smile much if at all. The only notable exception is the poster which shows her with a mysterious smile, having a finger over her lips, which is a sign of secrecy.

Despite her cute appearance, Maki is described as a hostile misanthrope of few words. She is very aware that she comes across as unfriendly and prefers to be alone. In general, she dislikes people and thus she is not very cooperative and can be stubborn. She talks very little, so when she does, she states things clearly and she appears to be very confident about her arguments. She is cynical and negative with a sharp tongue and sometimes talks in a cold sarcastic manner. While not the type to assertively act on her own, she is stated to have guts and willing to take action when it suits her. She has no problem blaming Kaede Akamatsu coldly and rudely multiple times. She was also shown to be very openly irritated by people who believe in the supernatural, such as Kaito's fear of ghosts and Korekiyo's seances. She bluntly told Korekiyo that she finds his beliefs stupid right to his face.

Despite her extreme personality, Maki actually holds deep insecurities due to her past as an assassin. As part of her training, Maki was forced to undergo torture, and stated that she "vomited every day" and "cried every night." According to Maki, she did at one point feel anger and pain for being forced to kill others, until she reached the point where she felt "empty", telling Shuichi that she no longer considers herself human. As a result, Maki's experiences caused her to feel hate for herself, believing she was not worthy of having friends and therefore deciding to distance herself from the other students. However, after befriending Kaito and Shuichi, Maki decides to try and change her perspective, eventually learning to accept herself like Kaito encouraged her to.

Despite her distant and unfriendly personality, Maki is good at taking care of others. She is very popular among children, even though she dislikes them. According to Kaede, Maki is actually capable of deep love, something that children might be able to see, explaining their attachment to her. She also shows a more caring side when she accepts gifts and is invited by Kaede to spend time together.