Lucy Maria Misora, also known as Ruuko Kireinasora, serves as a central character throughout the "To Heart 2" series and the OVA "To Heart 2 AD Next." An extraterrestrial originating from the third planet "ruu" in the constellation Ursa Major 47, she transfers into the human school as a foreign exchange student following her initial encounter with protagonist Takaaki Kouno, becoming his classmate.

She possesses distinctive lavender hair reaching her waist and crimson eyes with a subtle purple hue. Her standard attire is a pink sailor-style school uniform featuring long sleeves, a white-lined red collar with a double neckerchief-like ribbon, red cuffs, a red miniskirt with white linings, black socks, and brown shoes. Alternative outfits include a maid dress with an apron, headdress, and knee-high socks.

Her personality is self-indulgent, enigmatic, and idiosyncratic. She exhibits the ability to communicate with animals, consistent with her claimed origins. Her speech patterns are notably unique: she initially communicates in an unintelligible "starfish language," adjusting her translator by tapping her head to become understood. She frequently raises her arms while uttering "rū" (るー) and refers to humans as "ū" (うー). She occasionally speaks in third person and repeats words.

Across official media, including games, the anime series, and OVAs like "To Heart 2 AD Next," she maintains a consistent narrative function as a supporting character interacting with Takaaki and classmates. She appears in "AD Next," though specific activities or development details remain unelaborated. Her background remains focused on her alien identity and integration into human society, without significant evolution or additional backstory in sequels or spin-offs.

Her stated birth date is February 30, a date absent from the human calendar, further emphasizing her non-human origins.