Other people.

Two other girls to be specific. You wipe the cum on your tits and wave.

"Hiya!" You say.

The janitor looks up in shock.

"Michelle? What are you doing" One of them screams.

"I - uh - how long have you been here?"

"We saw everything."

"Even the -" You ask.

"We've been here the entire time." The other girl says.

The janitor quickly starts to redress and tries to exit the change room.

"We're telling the principal." One of the girls adds.

The janitor looks back at you and runs from the room.

You slip your sundress back on and reflect on the situation.

"Okay, go ahead. I don't really care."

"We'll see about that."

They rush from the room. You stand there, cum dripping down your legs. Despite all that's just happened, you're still enjoying the afterglow of your orgasm.