Maki Miyahara possesses black hair typically arranged in waist-length twin tails with spiky bangs. Her eyes are red and Tareme-shaped, complementing a slim, pale figure standing 149 cm tall with measurements of 78-56-82 cm. She favors casual and summer clothing like miniskirts, sundresses, sleeveless dresses, and pajamas, often adding hair ribbons or ties. She is commonly seen barefoot or in flip-flops.

She is the biological younger sister of Tomoki Miyahara and Anna Sanjou's cousin. Maki resides at Kawarazaki Manor with her brother and other family members, identified within the household structure as a non-blood-related daughter. Her interactions are friendly.

Within the cyclical events at Kawarazaki Manor, Maki becomes entangled in the distorted experiences alongside Yuuma and Anna. Her actions during the repeating two-day timeframe include engaging in a passionate physical relationship with Yuuma, contributing to the psychological tension and aberrant events unfolding within the mansion.