In Yukiko's case, it's all about the top and the bottom: Her eyes and hair at the top, her pantyhosed legs and butt at the bottom. She's a bit shy and difficult to approach at first, but can open up with some effort, or she can be taken by surprise without a lot of trouble so long as she's alone. Utilize smooth ropes or something that won't damage her clothes when tying her, and either give her a rope shibari or bind her legs beneath her skirt as she likes either one. For her gag, use anything that focuses on her eyes and secure it either over or under her hair. Once she's secured, leg rubs and hair stroking will keep her content.