Cuckold slave
Why would you want to see her get used by another man? It shouldn't excite you to imagine being tied in the corner while you watch your girl accept another man to fuck her. You know she must be curious what it is like to be dominated by someone who doesn't love her... Someone who is going to simply use her as a means to get off. He will no doubt use every single hole she has without caring how you feel about it.
Give me 100 strokes to just the head of your cuck dick.
As a matter of fact you must be a little bit of a sissy to want to see her used in such a way. I think you need to go and grab a pair of your girls panties. You know what? Make that two pairs of her panties. One fresh pair and one used pair.
Continue with full strokes while you anticipate what you are going to do next.