Sorin was drowning in pleasure. The unforgiving pace of Andrei's hips erased all the remnants of Sorin's inhibitions, his caution, and set him off. Andrei was like a hot live wire, dangerous to the touch, but Sorin had touched him anyway. This was the essence of his initial attraction to Andrei, that he could be so deadly, scary even, but it only excited Sorin. That decision to expose himself to something that could and should hurt him, voluntarily reaching out and wanting him, it was an empowering thing for the young witch. Something a psychiatrist would probably have a field day with.
What really cinched it for Sorin was that despite all this wild raw power, Andrei had himself under yoke. Capable of death and destruction, built for it even, Andrei likewise chose not to. He had control. He had feelings and emotions that Sorin wanted to see, wanted to embrace. Andrei's relentless movements, the sound of skin smacking against skin like a staccato drum moving as fast as Sorin's heart, it had the desired effect and the witch came undone.
His jumbled words - a mixture of Romanian, Serbian, and English curse words and compliments - were lost against Andrei's mouth as he kissed him and the next shift of the vampire's hips tipped him immediately over the edge. Sorin was so close anyway, it really didn't take much. He let go with relief, his body clenching tight as pleasure touched every inch of him, made his toes curl, fingers flex. Sorin's head tipped back, neck exposed and bite already bleeding as he came with a loud cry of Andrei's name.