Kei operates as one of three female assassins concealing their lethal profession behind the popular musical group, The Pussy Cats. Her assassination method relies on exploiting physical attraction to seduce targets, engaging them in a predatory game before she shifts into her lethal leopard form. In this feline state, she dispatches victims using razor-sharp claws and teeth, inflicting fatal wounds and consuming the remains. Her blonde hair and green eyes significantly aid in luring targets.

Professionally, Kei works alongside fellow assassins Sonya and Lukish (Lou), all directed by an older woman skilled in alchemy who manages their missions. Kei faces a profound personal and professional conflict when assigned to eliminate Magic Gray, her romantic partner. This internal struggle intensifies after she witnesses Gray with another woman. Despite the emotional turmoil, Kei executes the contract. She transforms into a leopard, attacks Gray, and consumes him, fulfilling her obligation.