Mirai Kuriyama, the sole survivor of her clan exterminated for their heretical power to manipulate blood as weapons, carries cursed blood that earned her shunning and reinforced her self-perception as a monster. A traumatic childhood accident, where she killed her possessed friend Yui Inami during a Hollow Shadow youmu confrontation, cemented her deep guilt and fear of harming others. This drives her isolation and hesitates her duty as a Spirit World Warrior to hunt youmu and sell their stones for income.

Following the Hollow Shadow incident, her revoked duties caused financial hardship, forcing her into temporary part-time work, including modeling and collaborating with Mitsuki Nase. Initially viewing the immortal half-youmu Akihito Kanbara solely as practice to rebuild her confidence, she repeatedly attacked him with her blood sword. His persistent efforts to befriend her gradually eroded her emotional barriers.

Her development focuses on confronting insecurities and overcoming isolation. Through interactions with Akihito—a fellow outcast sharing similar struggles—and the Nase siblings, she begins accepting friendship and support. Key milestones include joining Akihito's Literary Club, participating in group activities like the Lantern Festival, and cooperating with Mitsuki against youmu. These experiences foster trust and lessen her self-loathing. During the Hollow Shadow incident, she deliberately wielded her corrosive blood to inject Akihito and expel the possessing youmu, prioritizing his safety despite her own terror.

Her personality includes quirks such as frequently uttering "Fuyukai desu" (how unpleasant), maintaining a blog, expressing interest in bonsai trees, social awkwardness, and physical clumsiness. While her core earnestness and guilt remain, her journey shows growing confidence in both her abilities and her relationships.