A vast, deep lake near the Forest of Magic in Touhou. The Scarlet Devil Mansion sits either on the far side, or on an island in the middle of the lake - canon is inconsistent on which. Fairies Cirno and Daiyousei live on the lake's edge, and mermaid Wakasagihime lives in the lake itself. It's believed Rumia also lives somewhere in the area.
Initial setting and stage 2 environment for Embodiment of Scarlet Devil and stage 1 environment for Double Dealing Character.