Mt. Shumon (朱門山, shumongin) is a fortress lying in the western lands of the Hidden Realm and is the home to the Tengu. The Tengu have a most important trasure: the Tengu Fan. In order to protect their treasure, the Tengu have a tradition involving strict discipline. While the culture of their land is conservative, another aspect of the Tengu is that they are greatly fond of drinking and feasting.
Mt. Shumon is brought up in episode 2, when Matsuba offers to pay off Aoi's debt to Odanna and invites Aoi to live with his family and him.
- Shumon (朱門) is written with shu (朱), meaning vermilion or scarlet, and mon (門), meaning gate.