Rinne Amagane is a cheerful, energetic teenage girl starting fresh in a new town and school. Rushing on her first day to avoid being late, she stops to rescue a cat and is struck by a truck. This transports her to Death River Academy, a school in Hell, though she remains unaware she has died. Instead of despair, she feels determination to make the best of her situation, driven by a promise to make friends and her mother's teaching that strong will conquers any obstacle.

Rinne possesses light blue hair and blue eyes. She stands out in Hell because she retains her living human body, revealed when an injury causes her to bleed—impossible for souls lacking physical blood. This anomaly attracts attention, including from the human-appearing student council members who realize she isn't truly dead. Her personality is marked by relentless optimism, impulsiveness, and acting on instinct before thinking. She openly expresses her emotions and refuses to give up.

Isolated as the only human among demon classmates, Rinne persists in trying to befriend them. She forms a significant bond with Steela, a taciturn, feared, and ostracized classmate. Rinne defends Steela from bullying, demonstrating loyalty and empathy. Steela reciprocates by protecting Rinne multiple times, motivated by Rinne's kindness. Rinne also interacts with the student council president, Ryu Kutou, who initially appears supportive but conceals his true intentions.

Rinne's background deepens when she is revealed as the reincarnation of Eve, the biblical first woman. Ryu Kutou is exposed as Abel, Eve's son, scheming to exploit Rinne's identity. Abel aims to break her will, believing her unwavering determination and ability to inspire others stem from her connection to Eve. Despite enduring psychological and physical trials designed to crush her spirit, Rinne's resilience never falters. Her core strength lies in inspiring belief in others, empowering them through her faith in their potential. She adamantly rejects sacrificing anyone, insisting everyone can be saved.

During a school-wide volleyball tournament orchestrated by headmaster Hellvis (later revealed as Cain), Rinne's team wins, granting her a wish. She uses it to prevent Steela's hidden power—erasing souls from existence—from causing Steela's own annihilation. Rinne's intervention, combined with her unwavering belief, negates this fate. Conflict escalates when Abel enacts tyranny over Hell. Rinne's influence becomes crucial in rallying others to resist, ultimately dismantling Hell's existence—revealed as a self-inflicted construct perpetuated by Abel's grudge against humanity.

In the resolution, Rinne returns to the human world but loses all memories of Hell. Residual emotions persist, manifesting when she instinctively calls a young girl she saves "Steela." Rinne continues her life with renewed optimism, while Steela is implied to watch over her in gratitude. Though Rinne's conscious memories fade, the emotional essence of her journey remains.