Meroune Lorelei, or Mero for short, is a mermaid bound to a wheelchair. While she is the the fourth girl to officially move in with Kimihito, she is technically the fifth girl to move in with him because Suu was supposed to be the fourth but she lives there illegally so she doesn't count yet.

Mero has a very warm personality. According to Centaurea, she gets a vibe of royalty from her.

As a young girl she had a fascination with the "tragic love" story of H.C. Andersen's "The Little Mermaid," and wants to experience it in real life, even up the point of turning into sea foam (She want to be a lover instead of a bride).

(Source: Monster Musume no Iru Nichijou Wikia)