Always Fight the Enemy with Fists

A young man who knew nothing about his past came into a completely unknown world. He didn't know who he was, but he was full of inexplicable excitement about the battle. The instinct of his body seemed to be telling him everything he didn't know. But the most deadly danger was right next to him. World travel story, the first world is Shana of Shakugan, the subsequent world is to be determined.