Unico is a unicorn from Greek mythology, originally the companion to Psyche, a mortal girl whose beauty provoked Venus' jealousy. The goddess commanded the West Wind to banish Unico to the Hill of Oblivion. Instead, the West Wind transported Unico across locations and time periods, erasing his memories before each relocation to evade Venus and the pursuing Night Wind, creating a cyclical existence.

He possesses white fur, a pink mane, distinctive cinnamon-bun-shaped ears, and is often depicted wearing eyelink. His core ability generates happiness in those nearby when he feels genuine love. This emotional connection unlocks his powers: extending his horn for defense or healing, flight, and transformation into a winged unicorn. Losing his horn depletes all power.

During his journeys, Unico aids diverse characters. He helps Chao (renamed Chloe in recent adaptations), a black-and-white cat abandoned by her owners who dreams of becoming a witch's apprentice; she later gains human transformation abilities through his intervention. He bonds with Beezle, a lonely devil child on the Island of Solitude who initially resists friendship after mutual rescues. Later, he assists Cheri, a human girl whose family falls victim to Lord Kuruku's living puppet curse, confronting this antagonist born from a discarded puppet's hatred.

His stories incorporate ecological themes. He encounters Chiko, a girl suffering from pollution-induced illness, and combats the responsible factory. He also collaborates with Astro Boy and a tree spirit named Tsubasa to reverse environmental degradation by altering human actions in the past.

Despite perpetual displacement and memory loss, Unico remains defined by innocent compassion, using his powers to alleviate suffering and forming deep, transient bonds.