Kei Kakiba

Kei is a student at Kyoto Akanebara High. She's very pretty, highly intelligent, and shows a playful personality among those she trusts. She becomes involved with Reiji and Getsu following a dangerous incident involving a Mythical Beast and a Phantasm. Afterwards, she becomes friends with the two boys and works with them as cleaners for Beast Tech's "Fantastic Sweeper" branch.

Unbeknownst to herself, Kei is a Magus: an individual capable of witchcraft and high-level mysticality, the likes of which cannot be recreated using Monster Tonics.