Milk inhabits a house shaped like a baby bottle, presenting as a five-year-old girl. Her status as a superhero remains unconfirmed, potentially possessing only heightened agility and strategic intelligence. She displays selfishness, vanity, a short temper, and frequent drooling, occasionally tempered by compassion. Her relationships with the President—who assigns missions—and robotic maid Tetsuko fluctuate between affection and antagonism. She arbitrarily accepts or disregards the President’s directives yet invariably takes credit for mission outcomes, celebrating with sushi regardless of participation.

Notably cunning, Milk engineers intricate schemes and manipulates perceptions to achieve goals, often exploiting her youthful appearance. Despite this, childlike habits endure, including drinking powdered milk from a bottle. Recurring behaviors involve creatively evading the landlord’s rent collection and misusing a time-travel device to replay favored moments, causing unintended temporal loops. Her possessions include a Kakuei statue, and activities span video games and table tennis.

Documented media—spanning 1998 shorts and a 2000 series—shows no evolution in her personality or circumstances. A reboot, "Super Milk Chan Forever," was announced in 2021 but remains unreleased. Canon materials provide no additional backstory, family history, or character development.