Mimi Katsura attends elementary school alongside Illyasviel von Einzbern, belonging to Illya's circle of friends including Suzuka, Nanaki, Tatsuko, Miyu, and Chloe. She holds the position of an honor student at her school. Her background remains mostly undefined, though she possesses a younger brother who worries about her. Fundamentally sweet and kind, Mimi exhibits a strong considerate nature towards others. This kindness becomes a personal vulnerability, leaving her susceptible to Kuro's mana drainage. A significant character shift occurs after she witnesses a misunderstanding involving Illya, Chloe, and Miyu. Introduced to doujinshi by Suzuka and Suzuka's older sister, Mimi subsequently develops an intense passion for boys' love (BL) content, transforming into a hardcore fujoshi. This fervor manifests in delusional or uncontrollable behavior, causing her friends to deem this aspect a "lost cause." She possesses no supernatural or combat abilities, depicted as an ordinary elementary school student. However, she later cultivates a specific talent for writing BL doujinshi scripts, directly inspired by her misinterpretation of the Illya/Chloe/Miyu incident. Mimi is also portrayed as having an exceptionally weak presence, a trait used for comedic effect, resulting in her being frequently overlooked or forgotten. Within her friend group, she is particularly close to Illya. Her fujoshi activities involve creating BL material based on perceived homoerotic subtext between Shirou Emiya and Issei Ryuudou. Mimi appears in various installments of the *Fate/kaleid liner PRISMA☆ILLYA* series, including the OVA *Prisma☆Phantasm*.