Amiru Sumeragi attends Meigetsu Girls High School, presenting as a blonde-haired, brown-eyed student who favors twin braids. Her standard uniform includes a light purple blouse, purple jumper skirt, tan stockings, and black slippers. Upon transforming into her Reflector form, her attire shifts to a purple dress with yellow sleeves and overlays, complemented by long black boots, while her hair turns ashen grey.

Initially possessing a clumsy, lively demeanor, Amiru undergoes a drastic change when an accident strips her of all emotion. This incident is later attributed to Yamada Niina removing Amiru's Fragment, the manifestation of her feelings. Motivated to restore Amiru, her close friend Ryoka Tachibana becomes a Rogue Reflector. Amiru subsequently follows Ryoka's lead, also becoming a Rogue Reflector aligned with Mizusaki Shino's objectives. In this form, she wields chakrams, bladed ring weapons suited for long-range combat.

Her narrative unfolds through key interactions and choices. Ryoka discloses their shared past and the accident's impact to Hanari Ruka. Together, Amiru and Ryoka commit to returning stolen feelings to their rightful owners, signaling a shift in purpose. During this time, Amiru specifically requests a conversation with Ruka, seeking to understand her viewpoint—a notable engagement despite her emotional void. Amiru further supports efforts to confront Shino and address the conflict threatening the world and the Common, her actions consistently tied to Ryoka's choices and their shared goal of rectifying the consequences of stolen Fragments.