It's an RPG, with a turn based combat. Playing as sage in a shrine, you have the ability to exorcist Ayakashis(Japanese's supernatural monsters/beings) and also the the ability to befriend and make them as you familiar so they could fight alongside with you and guard the shrine from invasion. Like in any other RPGs, you'll get quests from troubled villagers to exorcise for them, though you also have a choice to spare them and let them in your group.

You form your party consisting of the Ayakashis you took in, each of them will have different abilities and personalities. They are tough creatures so it is recommended to befriend them quick. They'll also need your affection, if you have a high intimacy point they'll have a boost of power.

Intimacy point can also decrease over time, and they'll probably stop being your friend. But rest assured it'll drop down slowly, but it doesn't mean you can just neglect them. Choose your familiars wisely!

PS: There's also a Ayakashi Collection gallery for those who are interested to collect them all.