As Nariyuki's younger sister, Mizuki shares a strong physical resemblance to him, having the same facial features as his (though hers are slightly more feminine). Mizuki's black hair is styled in a way that frames her face at the same time it is tied in a ponytail. Her breast is little bit large, much larger than Fumino.
During the week, Mizuki mostly wears a middle school uniform, while at home she wears an apron with printed words.
She has a serious brother complex, and mostly prepares housework for Nariyuki at home.
- She prepares lunch and dinner for family members.
- She is good at housework.
- Her aprons are printed in different English messages.
- Her school uniform is same as Uruka at middle school, later revealed to be a student of Nanao Municipal Middle School.
- She knows Kobayashi in childhood, and later Oomori.
- She participates in swimming team, admires Uruka.