Etoranze ~Uchi no Pet wa Neko no Kami-sama?~

Main character's sister returns from a distant town on the first day after summer vacation. There is nothing special in the return itself, but the strange thing is that she is possessed by a cat God. The deity promises to return sister's personality is protagonist helps with finding and hunting monsters. But the real problem is that she messes with everyone turning ordinary life into chaos.

[Modified from vndbreview]