This is a bit of a fantasy setting, so I created a restraint device with similar style, for this original story.
These magical chains, are bound onto her arms, and she can use them normally like there's nothing, until the device tightens the chain, pulling them into positions, eventually restraining them behind her back.
It is attached to her back like a simple belt harness, it can be easily taken off when she is not restrained, the question is, why doesn't she?
Edit: Forgot to mention, I wanted to use the dark elf skin, it goes really well with the red chains, after some fine tuning.
Have to say, we gotta do more of the models from RyanReos, they are too hot.
Model by @RyanReos