From Kirei Cake:

Miko, a young girl from the north, finally manages to visit the city for the first time. She came in hopes of finding her older sister, but gets lost instead. She finds a cat scaling the handrail of a bridge, but it accidentally falls off. Miko tries to save it, but instead she falls off herself. When she wakes up, she realizes that she's actually already dead, but the cat had saved her with one of its nine cat lives. Unfortunately, a cat's life only lasts for a year, and Miko needs to figure out a way to get her original life back, as well as a way to somehow find her sister.