The promise is to have three good qualities: delicate body, soft body, easy to push...
Promise: Push the ball! (*｀ﾛ′ﾉ)ﾉ If you continue to be cowardly, you will be bullied to the point of being bullied! !
All in all, it's a story about a soft-spoken girl who struggles hard in various worlds and develops into a tomboy without looking back.