You have a fascination with your giant stepaunties large belly, She is a bimbo of very little brain and agrees all the time to let you play with her privately on her belly. You tell her you want to cum in her belly and she agrees, but lets you bounce on her first hearing to tummy slosh. She swallows you for you to cum in her belly, and as you slosh around inside of her she feels guilt and doesn't want to let you out...oops.