Luna Tsukuyomi is a 12-year-old girl with waist-length light green hair and yellow eyes. Initially shy, quiet, and introverted, she preferred solitude and existed as an outlier within her friend group of Seira and Ginka before Akari Taiyō's arrival, finding social connections difficult.

As a member of the Tarot Card-themed group "Sefiro Fiore," Luna wields the elemental Moon Arcana, specializing in manipulating light and illusions to protect others from dark forces. She gradually accepts this responsibility as her confidence grows.

Luna actively seeks friendship with Akari, the new Sun Tarot card user. Over time, deeper romantic feelings develop, though she struggles significantly to express them verbally. Her kindness manifests subtly: wanting to know more about Akari, caressing Akari's bangs while she sleeps (and panicking when Akari wakes), and sleeping next to her, indicating a desire for closeness.

Beneath this kind exterior, Luna harbors intense jealousy. This emerges strongly when Seira forms a closer bond with Akari after resolving their differences. Consumed by envy over their connection, Luna becomes vulnerable to manipulation by the antagonist Cerebrum. This leads to her transformation into a demonic wolf hybrid, during which she attempts to kill Seira, driven by distorted emotions. After reverting to human form, Luna expresses profound regret, marking a pivotal moment of self-awareness and growth where she consciously works to overcome the jealousy within her heart.

Her character development revolves around navigating complex emotions, particularly her affection for Akari and envy towards Seira. The experience with Cerebrum serves as a catalyst for confronting her negative traits. She evolves from a withdrawn individual into someone more determined to protect her friends and confront darkness, demonstrating increased resilience and emotional maturity by acknowledging her flaws and striving to improve.