Nega, an alien from Featherstar stranded on Earth in feline form, partners with Posi to monitor Yuu Morisawa after she gains magical abilities from Pino Pino. Their mission prevents Yuu from exploiting magic for selfish ends, like cheating on exams. True to his name—short for "negative"—Nega embodies cynicism and pessimism, starkly contrasting Posi’s optimism.

As a mentor, Nega knows advanced magical incantations but deliberately withholds them to curb Yuu’s temptation. She occasionally outwits him into revealing secrets, such as conjuring a truth-telling pen. Lazy and irritable, he avoids duties through sleep or sarcastic quips, often targeting Yuu or Posi for comic effect. Yet beneath his gruff exterior lies deep affection for Yuu: he tearfully dreads their eventual separation and once mistakes another girl, Cassidy, for her due to his attachment.

Nega intermittently takes center stage in episodic arcs, collaborating with Posi to guide Yuu through supernatural threats—ghosts, interdimensional beings, and cosmic entities. They also guard her secret identity as Creamy Mami, knowing exposure would strip her powers. In the 1985 OVA, set after Yuu’s magic expires, his role diminishes, though his bond with her endures. Throughout, Nega balances his prickly mentorship with loyalty and hidden vulnerability.