The Rising of the Shield Hero by Aneko Yusagi

At a critical moment, Naofumi and the others are saved by a young girl. Ost’s sacrifice is enough to save them from their battle to the death with Kyo, but Kyo's able to escape to another world. Naofumi attempts to follow him, but he awakens to find himself in prison! His friends are scattered and he finds himself back at level one. How will Naofumi survive the new challenges that await him?