Mizuki Tsujimura is an agent of the Special Division for Unusual Powers and she is assigned to Yukito Ayatsuji. She is the deuteragonist of the spin-off novel. She wields the ability Yesterday's Shadow Tag. Mizuki has light cyan hair which is parted to the left, part of which she keeps in a ponytail, and lavender-purple eyes. She wears a white neck scarf patterned with the same cyan hue, a white dress shirt, a gray suit coat which she keeps unbuttoned, and gray slacks. She also wears gray gloves, black heels, and a dark gray belt. During her teenage years, she had short hair with the same bangs swept to the left side and she wears a standard seifuku. Tsujimura appears as a kind and genuine woman, although slightly gullible as shown when Yukito Ayatsuji tricks her in making him coffee. Tsujimura is also very dedicated to her job and respectful to her seniors. She also considers herself confident in her job and even describes her performance as top-notch and having more drive than anyone. She is also sets a goal for herself, even telling herself that she needs to catch up to a movie heroine - a spy who wear bicker jacket and glasses. She always show her "strict" side when trying to reprimand Ayatsuji when he does as he pleases but constantly struggles to get Ayatsuji to follow protocol. Feeling strongly about her duties, she often gets swept up at the moment.