Together with her partner and love interest, Takuto Kira, Meroko Yui is a part of the shinigami team Negi Ramen, sent to collect the soul of 12-year-old Mitsuki Kouyama.

Meroko is a rabbit shinigami with long ears, and she is capable of transforming into an anthropomorphic bunny stuffed toy.

She has a hot temper and is sometimes very moody especially when it comes to her relationship with Takuto (despite her constant attempts to impress him, he doesn't seem to notice her or have the same feelings).

Though she tries to help Mitsuki with her singing career, her ideas often get the girl into trouble.

In the anime, she is rather fond of changing her appearance into other characters, and her trademark phrase in the anime is "Mero Mero Change!"