He wants to react, but while Natasha just watches him, her eyes feel like the bore into his. All Bucky can do is stare back. He does manage to lift his other hand, and softly swirl it down her stomach, just feeling.

When she guides his cock, just grabbing it brings short, pleased moan from him, and he, lightly, pushes his hips up, just to help the motion along. Both of his hand slip down to her hips, and while he's careful not to hold her too tightly, his grip is firm.