Milcatopy is a side character in Kyouran Kazouki Nikki who appears to be a regular cat. One rainy evening Rindou Katsura picks her up in the rain and brings her home. In the morning she becomes a human (not explained) and ends up working with Rindou at the Virgo bar.

Milcatopy, for the most part, is a cat-girl and is very naive and young at heart. Despite this she and Rindou form a very stable romantic relationship.