Tatsuki Mori, also known as Mori Tatsuki, is a 15-year-old Lily affiliated with the Alfheim Legion at Yurigaoka Girls Academy. Born on July 22 with blood type B, she stands 163 cm tall and weighs 49 kg, distinguished by her light blue hair and purple eyes.

Her personality is notably eccentric, influencing both her thoughts and combat approach. Initially shy and avoiding eye contact during first meetings, she becomes talkative once comfortable. She shares a close bond with Araya Endo and Misora Kanebako, who aided her through side effects from enhancement procedures.

Rescued by Yurigaoka as a junior high student, Tatsuki now works in the Arsenal Department, crafting CHARMs exclusively for her own use. Her combat style reflects a one-man army mentality, prioritizing individual action over team coordination.

She possesses the rare skill Lunatic Trancer, enhancing her combat capabilities, and uniquely hears the voices of Huge—the extraterrestrial threats faced by Lilies. This ability stands as a distinctive trait.

Her name derives from "tatsu" (dragon) and "ki" (princess), while her surname "Mori" means "forest." She operates within the established framework of Alfheim's activities.