Erwin lets Levi push him onto his back. He's not quite sure where Levi is going with this, but he's certainly not going to complain. Just as Levi apparently likes it when Erwin picks him up and moves him around, Erwin likes it too; he knows Levi is more than capable of throwing him all over the treehouse, and the thought of him doing exactly that is pretty damn hot.

When Levi plants himself on Erwin's lap, Erwin's hand immediately goes to Levi's thigh, caressing along the muscle there. Levi isn't big the same way Erwin is, but his muscles feel like iron cords under his skin, and Erwin is going to shamelessly appreciate them. He's also going to watch Levi take his shirt off, and while Levi isn't trying to be sexy, it's one of the best shows Erwin's ever seen. All this is glaringly apparent in the way Erwin is smiling, his eyes bright and attentive, watching the show.

"I'd do the same for you, but..." But yeah, only one hand, and given the choice between using it to grope Levi's thigh or taking his shirt off, Erwin is going to choose the thigh every time. At least, he'll choose the thigh until Levi's shirt is open, at which point he's going to move his hand up Levi's hip and to his abdomen. The ready supply of sugar and fats in this world has been settling on Erwin's midsection, but Levi still looks as trim and fit as he did in their own world.