A hannya is actually a mask, not an oni demon. People mix them up. The hannya represents a woman consumed by jealousy and resentment who’s been transformed into a demon.

There are different ways you can render the color and features to show how deep into that transformation the woman is. More demonic, less human. They’re associated with being able to love deeply and also being able to be totally consumed by passion, whatever the sort.

Like most Japanese imagery, the duality is built in. Getting a hannya might mean you’ve had a battle with that feeling, or it might be there to protect you from having to. Or both. I usually pair a hannya with something pretty to add the yin to the yang. Even with the grisliest scene, I want it to be visually appealing from a distance. Extra important with bad vibes like a hannya.