Suddenly her rear clenches. Her entire rump quakes and her vulva opens wide strong muscles pulling against his arms. A wave of fluid sprays across his chest and head soaking him. Pushing hard he feels the walls grip his head pulling it deeper into her. His shoulders ram against her attempting to force her wide enough to enter. Once they are inside past her outer barrier she will feel fuller then she ever has. Even more then when she last gave birth. The pressure will be immense at first, painful even, but her pleasure should overwhelm the pain, in time.