Miu Kohinata stands petite at approximately 145 cm tall, with a slender physique reflected in measurements of 73 cm bust, 50 cm waist, and 75 cm hips. She possesses brown eyes and distinctive neck-length purple hair. As one of three stepsisters in the Kohinata family, she became the second-eldest daughter when her mother Yukie remarried Akira Kohinata's father.

Miu exhibits a docile and introverted personality, characterized by shyness, frequent embarrassment, and reserved behavior. A defining trait is her strong emotional attachment to stepbrother Akira Kohinata, demonstrated through devoted and earnest affection toward him.

Within the family, she interacts with eldest sister Yuki Kohinata, third-eldest sister Nana Kohinata, mother Yukie, and stepbrother Akira. Her role in the central narrative involves Akira's supernatural task—mandated by the goddess Inana after her accidental summoning via an artifact from Akira's archaeologist father—to collect specific bodily fluids from his stepsisters, including Miu. This mission must be completed before the next full moon to prevent dire consequences.