Adam.

There was only one item in the box and a piece of paper.

The costumes were selected at random and each year there were cool costumes and others that were less comfortable for those wearing them.

It was a green fabric fig leaf, with a small pouch behind it. He would have to slip his dick and balls in the pouch and the elastic band would keep it and the leaf in place.

Of course that meant that while his privates would be kept hidden he would still have to attend the party totally naked.

Due to his strange behavior regarding clothes he had stripped before hesitating on putting the costume and had stood naked in his room all this time.

The thought that if he was Adam there would maybe be an Eve at the party was a big bonus and he had trouble figuring how such a costume would work on a girl. It could even be Emily that received this costume, or Samantha?

He couldn't resist the temptation. He put the leaf in place, the pouch encasing his private parts snuggly.

He went out of his room to wait for his sister. It was almost time to go.

She went out of her room dressed as Pocahontas, with a top and skirt made of deer skin, with a few pearls and feathers in her hair.

"OMG! You drew Adam? This will be so fun. You're lucky, this costume has a lot of success with the ladies. " she said to him. Emily had been invited to those parties before, maybe she knew thing he didn't. The idea of having success with ladies was enough of a boost to his ego to make him follow his sister out of the house.

She had arranged for friends of hers to pick them up in their car. (neither of the twins had a car despite both having their driving license, their mom didn't judged them responsible enough).