This game is the one I've been waiting for... a mimikko nakige that doesn't ignore the setting or human nature. At the beginning of the story, the protagonist, Kazuki takes in a puppy he finds abandoned in the park, feeds her, and then falls asleep with the half-feral cat he feeds occasionally watching.  When he wakes up, they've both transformed into mimikko, a catgirl and a doggirl...  Soon after, it becomes apparent that shortly after this event, pets around the world began turning into