The 11th cat is Nene

In the land of the cat people, it is a serious crime for outsiders to enter without permission. However, Nene, a mouse-girl, has managed to sneak into the country with a mysterious goal. In the meantime, Nene finds work at the Rai Rai Teahouse. Working alongside beautiful cat-girls, she struggles to learn how to "be a cat" from her senpais. (Source: Natalie, translated)