/cgl/ - Cosplay & EGL

I'm making Maou's demon legs for Halloween, but I'm not sure how to keep them attached to my legs. As you can see in the picture, they stop mid-thigh. I'll probably have my pants go over the stopping point (not cosplaying just underwear, haha) so I could just sew attachments that would be hidden under the pants to hold them up, but I'd like the option to have them just… glued to my legs or whatever to hold them up if possible. I'm especially worried about moving around a lot in them and having them fall off my legs. Any suggestions?