Ryuuko knows how to fight and definitely knows how to avoid being kidnapped by force, but she can also be very reasonable when offered a casual binding. So long as she feels she can trust her captor, she's much more willing and tends to enjoy the situation quite a bit more. Her weak spots are both of her sides and are much more sensitive when exposed, so try and catch her in a midriff-exposing outfit. Her hair and eyes are both nice features to admire when she's gagged, so go with something that covers the lower half of her face. If she's kidnapped by force, expect a revenge attack sometime after she's freed.