Shinkage no Samurai, Academy de Musou suru

On Earth, a calamity known as the [Gates of Ruin] suddenly appears. From these gates, countless creatures pour forth, driving humanity to the brink of extinction. The ones who save the world are “Selectees” who form contracts with gods and heroes to gain supernatural power. Meanwhile, Hinata Kamio, a boy with no abilities at all, spends his days as a failure, enduring relentless bullying. In the depths of his despair, a mysterious samurai hero of unknown identity appears before him. Once the weakest of all, Hinata begins walking the path to rise to the top at the academy where Selectees gather.