I don't think this is NTR if it's consensual? Most NTR put you in a position of powerlessness when your significant other is dominated in front of you.
I mean its trading partners, with friends who you trust? So technically a "safe" space? Idk I'm not fully knowledgable about it, but I doubt its NTR.
That aside, I'm not a fan of the story, but I might as well just read it thru since I made it to this point.