Mizuki Inuhiko is a fellow classmate of Ouri Kagami at Ikai High School, alongside Hiroshige Ushijima, Sumitori, and Nozomi Kasuga. She serves as the student representative and is a member of the student council, with claims suggesting she is its only member. Aspiring to become the student council president, she dreams of reforming the entire school with the support of her friends.

Her name carries specific meanings; "Mizuki" combines the characters for "felicitous omen, auspicious" and "tree," while "Inuhiko" means "dog" and "boy" or "prince."

She frequently sucks on an unspecified object, which could be a cigarette or candy, though its exact nature and whether it is lit remain unclear. Often providing her friends with the latest city news, she favors stories with a mysterious touch.

In terms of personality, she is very observant and displays traits that are not very feminine, often acting in a rough and harsh manner. She possesses a strong character, confidence, and a motivating attitude that encourages those around her to persevere. However, she can become brutal when irritated by Hiroshige Ushijima, whom she seems to dislike despite being one of the few females not pursuing him. She strongly dislikes it when Ouri Kagami refers to her by her surname.

Physically, she has brown hair. Her eye color is described as both black and blue in different sources. Her typical attire includes a school uniform, a tie, and knee-high socks. She has a birthday of April 28, the Taurus zodiac sign, and blood type O.