Into a tunnel

You continue down the road despite the pressure still building within you, finally coming to a level area just before the entrance to a tunnel. Beside the tunnel's mouth hangs an old sign. Something is five miles away, but someone has sprayed paint on the sign in the image of a ejaculating cock. It looks almost as big as the plug inside of you feels.

The tunnel is dark. If any lights are in the ceiling, they aren't shining. You can definitely see a point of light in the distance, the other end of the tunnel, but it looks so far away.

You take a first step into the darkness and stagger as your pussy spasms around the device lodged within. It is trying desterately to acomodate or expel the massive invader. The leggings' crotch is soaked. Only the vague promise of release keeps you going. Only the fear that you might not be able to stand back up keeps you on your feet.
As you move deeper into the tunnel, you lose sight of everything. It is like being blindfolded. Without sight to distract you, the sensations within your pussy become your whole world, each movement blissful agony as you swear you can feel it growing with each step.
You stagger and close your eyes for a moment, trying to remain calm but when you open them again you feel a moment of terror, unable to see the light from the far end of the tunnel. But then you realise you were just turned around. It's there...