Keijo!!!!!!!!

"Keijo" is a popular gambling sport where contestants stand on platforms floating on the water and must use their butts and chests to fight against each other to push each other off the platform. Nozomi Kaminashi, a high school student, aims to join the sport after she graduates. Nozomi was raised in a poor family and hopes to make lots of money by playing Keijo. She grew up training in gymnastics, and she has good balance and flexibility.
After high school, Nozomi joins a training boarding school and enters the world of Keijo.
(Source: Anime News Network)