Eri Hanae is Kimito Kagurazaka's childhood friend. This 15-year-old high school student sports black hair typically tied in a ponytail with a large ribbon, purple eyes, fair skin, and average height. She often dresses in a light blue sweater, yellow skirt, black stockings, and brown shoes, or wears her school uniform.

Her personality presents a striking duality. Publicly, as an idol voice actress, she maintains a cheerful, innocent, and "moe" persona, referring to herself as "Eri-rin." This side appears kind, slightly childish, and reliant on others, especially Kimito. Privately, however, she reveals a mean-spirited, sadistic, and short-tempered nature. She speaks negatively about colleagues, expresses aggressive intentions during auditions, uses profanity, and mistreats Kimito—kicking him while labeling it a "foot job." Despite this volatility, she deeply cares for Kimito and only shows her true self around him.

Severe bullying during elementary school led Eri to contemplate suicide. Kimito intervened, enduring physical harm to protect her and spending months helping rebuild her self-esteem, fostering her romantic feelings. However, after overhearing a statement she misinterpreted as Kimito rejecting her ("I would never date her"), she grew resentful and began treating him harshly. In retaliation, she falsely spread rumors about Kimito being homosexual with a muscle fetish. This lie directly caused his abduction to Seikain Academy, which deemed him a non-threat to student chastity. Theories suggest the rejection statement might have originated from Kazuto, Miyuki's brother, due to a childhood identity swap between Kimito and Kazuto, though this remains unconfirmed.

Distressed by Kimito's sudden disappearance, Eri maintains contact with him via his DS. She later arrives at Seikain Academy herself, becoming the "second commoner sample" through an unspecified deal. Her primary motivation is to retrieve Kimito and return him home.