Ayumi Hizuki, a third-year student at Akizuki Academy, shares classes with transfer student Naoto Rindo. Her calm, homely nature makes her popular among peers despite lacking leadership traits. Academically gifted, she holds an A recommendation for university admission. After her sister Yuiko's marriage, Ayumi shoulders all household chores for the Hizuki family, drastically reducing her free time and preventing social or romantic pursuits despite her appeal. She personally shows little interest in seeking a boyfriend.

The Rindo family curse compels Naoto to conceive a child with a Hizuki to break its generational hold. When his intended fiancée, Suzune Hizuki, falls comatose after a car accident, her soul becomes trapped in a toy ring Naoto once gave her. Ayumi unwittingly hosts Suzune's spirit through this ring, experiencing intermittent possessions. To revive Suzune, Naoto and Ayumi engage in repeated intimate encounters aimed at conception, during which Ayumi develops genuine feelings for Naoto.

Ayumi eventually becomes pregnant with Naoto's child, creating profound inner turmoil. With Suzune's spirit still bound to the ring, Ayumi wrestles over relinquishing Naoto to reunite him with Suzune or fighting for her own relationship. Her pregnancy and emotional attachment complicate the original goal of breaking the Rindo curse.

She possesses long, straight brown hair and brown eyes, typically wearing school uniforms, sweaters, T-shirts, pajamas, knee-high socks, or sport bloomers. Her personality blends jealousy with a strong domestic inclination, particularly excelling in cooking.