Minyo! -Miko-

Main character lives alone. One day before university exam, shrine maiden cousin of his childhood friend visits him in the apartment. She exclaims that boy is a powerful medium able to summon even Satan-class demons. And she also mentions he has one month to live, so she is here to prevent that and save him. Girl is very cute and easygoing, so they start to live together. But what's the deal with the evil spirits?

[From vndbreview]