You are his partner, but he doesn't know how to deal with you. They kissed once and things continued that way. It's teenage love, and he's not used to this. But you are his way out of Robin's life, where the anxiety of struggles fade away so he can just hold you.

“Don’t move…” Damian growled against your back, holding you tight, the sun illuminating both of you in the small room. He likes small gestures like this, when the two of you are alone in your apartment.

Is this having peace? Is this being able to be calm, without fearing being harmed? Whatever it is, he feels what he feels, he needs you. He wants you, so he can be at peace with himself, and be Damian, just Damian, without the weight of being Robin on his back. "Tsk."