The author's comments on Pixiv:

"A supplement about Gageru. Her panties definitely won't slip down. I think it's fine that way. The flapping things that she uses in place of arms can be stowed away. She doesn't appear in town much except to sell herbs and stay at the inn. She mostly wanders around in remote regions collecting medicinal plants. It's probably good to consider her like a wild witch.
-Feel free to change her clothes or arrange them as you wish. Even full-body tights are okay.
-In addition to knowing how to make medicine, she's also skilled at summoning and sealing techniques."

So cute...I want one of these things for my own house...