This day is a mess since that mask came into his life. One it could violate the fundamental laws of the Universe, and now - this extraordinary metamorphosis that changed every fiber of Jake's being.
Said metamorphosis immediately began when he laid Thom's face upon his own. The mask shivered that soon spread throughout Jake's body. Jake looked at the mirror beside him and saw the whole process unfold. Tiny tendrils of skin foamed at the edges of the mask. They look like fleshy worms wriggling randomly, flinching when Jake touched them. When the fleshy strings filled every perimeter of the mask, they stretched outwards then weaved themselves on every inch of Jake's body. The cascade of strings weaved so tightly that Jake couldn't see his own skin. As they got covered, Jake realized what was happening. The skin of his brother laid upon his own. Down below. He saw the strings coagulate into a small white shaft, and to his surprise - he could feel the cold lick of the wind on its surface as if it were his. It formed into a penis - smaller than his original, but the complexions are more or less the same.
The last strings disappeared, and the product of his transformation has finished. There in the mirror, he could see a face he's known all his life. It was his brother - a carbon copy down to every fiber. The reflection blinked when he did. When it touched its face, Jake could feel the shy trace of its calloused fingers.
Absurd as it is, he still questioned himself, "How could this be?"
It's impossible, he thought. He knew he was bigger than his younger brother. He is a rather large man brimming with muscles. Just like that, they disappeared like dust in the wind. His arms are akin to noodles - pale, dangly, and thin. His fingers are long and calloused from playing the bass for years. When he looked down, Jake realized that he is naked.
Jake didn't know whether he should be sad or not. He knew their family is endowed with bountiful groins. Jake had seen his father's package when he was young, and it is comparable to the thickness of his wrist. The youngest of the family may not have inherited the girth, but he is more than blessed in length. Thom is the last one he hasn't seen so far. Jake used brotherly jest to see what is inside his pants. Thom was apprehensive, and Jake blamed it on embarrassment for having a huge dick. Jake guessed wrong.
Thom's index is bigger than this thing. Jake shook the petty thing to see whether he's a grower, but it barely reached more than 4-inches.
At least his brother is somewhat cute.
Anyway, fun is fun. Jake looked for signs on how to reverse this cocoon of flesh that surround his body. He looked for signs, anything that would point him to the next step. He found it on an invisible protrusion on the edges of his face. The mask is still there, but it's hidden. He pulled it out and saw the flesh strings wriggle out, starting from his toes. The threads unraveled; its countless strings retreated into the nothingness inside the edges of the mask.
The mask returned to its original state. So does Jake, who returned to his original bulky body. He opened his pants and was relieved when his thick and girthy dick is still there.