Deltoid

In the post-apocalyptic kingdom secluded from the rest of the world, there's a young boy who finds himself in existential crisis as reality starts to distort from his mind.

A frustrated high-school volleyball champion who lost his streak as he turned to college makes a deal to a being from another world to transport him back in time during his days of greatness. Beyond his knowledge, he was stuck in between the multiverse to turn volleyball into a bloody mess of a death battle.