An interesting story, but could really use some fleshing out.

For one, neither girl seems to have any distiction between them personality wise. And you could have done more to describe their bodies, and how that factored into their allure as they pooped. Also, more comedic dialogue could be used, like some people finding a poop battle different and strange from a pokemon battle.

Finally, it could use some spacing here and there, though at least you did well not to make it one big solid block.