You don't answer him. Not really. You just lean against him and tell him that you felt something. It takes him a moment to understand that you're referring to his previous statement about the Cas of this world rather than his question. When he does, he feels a twinge in his chest, an uncomfortable contrast to the pleasant tingling spreading out from where your hand is resting on his thigh. You felt something. But he wasn't there until it was too late.

He doesn't want to think about that. He doesn't want to think about you, the you of this world, or the fact that you're not a girl. He doesn't need to think about it. Shifts a little so he can slide his arm around your shoulders, tug you in a little closer against him.

"Let's just pretend right now, all right?" That's what you asked for. He'd like to do that. Pretend for one night that things went differently. Pretend for one night that it doesn't matter that you're a guy, that they can do this and it won't be wrong, or bad, or doomed. Pretend for one night that they can do whatever they want. They can go back to the real world tomorrow morning.