Mutsuki is kindhearted and gentle but starts off as shy with little self-confidence. Having constant bouts of anemia, ironically, Mutsuki feels repulsed by blood. Due to being sickly and his low self-esteem, he faces discouragement as a ghoul investigator to the point where he feels as though he is not even needed for the job. He expresses frustration with his own weakness, feeling anger at his lack of ability compared to his comrades. He is also later revealed to be a woman when fight Urie.