Basquash!

Basquash! is an original anime series that aired in 2009.

The series takes place in the world of Earthdash, an alternate version of Earth where society has split between the advanced lunar society and the regular humans on the planet's surface. A popular sport is Bigfoot Basketball, where players ride mecha and play basketball in a giant arena. In the city of Rolling Town, Dan JD wants to take his disabled sister to the moon for medical treatment for her paralyzed legs when one day, he accidentally revolutionizes the sport. However, while he does gain fame, he doesn't earn a trip to the Moon but instead has to fight his way to the top of the game while trying to solve a mystery that affects the future of the planet itself.

Episode 1
Dan appears naked, and he takes his shirt off after getting wet.

Episode 9
Dan is seen bathing at a hot spring.