Alien Baby Crashes to Earth

When the mother of astronaut Furutsuki Mirai has to go to America, Furutsuki Midori is forced to move into the Nishio family residence. There, in an extremely awkward situation, she meets Nishio Houkou, who lives there. Suddenly, a strange occurrence happens where a stuffed animal with a little cat on it appears. Houkou and Midori press the toy and it suddenly grows larger. It turns out that it's a nanny named Wan Nyaa, who takes care of a child named Komichi Kokoro. Thus, the three of them, along with the cat, form a small family at the Nishio household. Komichi even calls Midori and Houkou mom and dad. However, this secret cannot be revealed publicly; in front of classmates, Midori has to pretend that Komichi is her younger brother. Moreover, Komichi must not float in the air.