Do nothing.

The tentacles continue to stroke and caress you. They move up to your waist and buttocks, kneeding gently. Tentatively, one reaches out and touches the tip of your erect penis. As it pulls away, a drip of precum forms a small hanging strand. The tentacle retreats back to the orifice, flicking itself inside, then coming right back out. The creature visibly shudders and makes a pleasant, vibrating sound.

Other tentacles begin to touch your hard dick. All eight of them are now caressing your body. A tentacle wraps itself around your shaft, and begins to pump it very slowly, almost teasing-like. It's almost more than you can bear.

You start to move your hips back and firth, in time with the rythym. Tentacles wrap around your lower body, constantly moving.