Aoi, who inherited the ability to see ayakashi (supernatural beings) from her late grandfather, is suddenly taken away to Tenjin-ya, a long-established inn in the hidden realm where ayakashi reside. There, she learns that her grandfather once made a pact with the inn’s master, a powerful ogre god known as the Oodanna. The promise? To offer his granddaughter as the Oodanna’s bride as collateral for his own debts.