She snatches the marker and writes on you.

While you grab the marker and think about what to write, Stacey apparently isn’t happy with how long you’re taking. She snatches it out of your hand, leaned over your chest, still riding your cock with everything she has, and writes something on you. The problem is, it’s too close to your head for you to see it. Then she throws the marker away, grinning. “Thaaaaaat’s better.”

The effect becomes evident pretty quickly. From nowhere, your libido jumps back up to maximum, and your cock stiffens inside her pussy. Suddenly, you’re back in the game, and the fucking continues.

It goes on for quite a while, until you finally cum again. But it doesn’t stop there. You stay hard, and your lust doesn’t diminish in the slightest.

While you don’t know exactly what she wrote, the effects are pretty obvious. There’s no limit to your stamina now, or your horniness.

Combine that with making Stacey a nymphomaniac, and the two of you literally fuck for half a day, without stopping.

In the end, you only give up because you’re both getting sore and running out of lube.

Laying in bed, too exhausted to really move, you look over at your girlfriend, who looks more satisfied than you’ve ever seen her before. “The marker’s pretty good, right?” you ask her.

She laughs at that. “Understatement of the year.”

The only question is now, what will you two use it for?