Elsie is a demon from Hell assigned to capture escaped lost souls concealed within human girls. She forms a contract with Keima Katsuragi to aid this mission, enforcing their agreement with an explosive collar device. Her duties involve identifying targets and facilitating Keima's interactions to extract the souls by causing the host girls to fall in love.

Operating in the human world, she poses as Keima's cousin for cover. Her demonic traits include horns and a tail, typically hidden from human view. She works under the supervision of Hell's authorities, following their established protocols for soul retrieval.

The character maintains a relentlessly cheerful and energetic demeanor, contrasting sharply with Keima's reserved nature. Her enthusiastic approach to missions and literal interpretation of situations frequently contribute to operational complications. She exhibits a strong sense of duty regarding her soul-capture responsibilities.

Her interactions primarily serve to advance the central plot of capturing souls.