Lady and Nanny

“Have you heard of the mimic slug?”

The protagonist, a researcher of mysterious creatures, receives a suspicious letter. It was a request to use the mimic slug, which can transform into the appearance of others, to make it seem as though his deceased daughter had come back to life. Arriving at the mansion with a sense of foreboding, the protagonist found the “young lady” waiting for him.

(Source: Naver, translated)