Regardless of whether or not the two are actually dating, it is a NTR scenerio. Everyone at the party heard that she was a virgin, and kept the true meaning of the party from him until it was too late. They were actively trying to NTR him.
Not really, because the rule of the party was to go with your girlfriend/boyfriend to swap them, the girl lied about sora been her boyfriend so they let them participate, then the swaping started, Sora did it with the girlfriends of the other guys too, he was not just looking like a victim of a NTR do. So is not NTR, is just an orgy and Sora and the girl were just too popular because they were the newbies of the party.
