Survive in the Parallel World, Please! by NanaiSensei

Six heroes are called to a world where the human species is doomed to extinction with the sacred task of preventing it. One feeble and amnesic guy who has been abandoned in the bush without any means of life must take on the responsibility of leading them in their crusade.
Join Ryu on his slow-moving trip through a fantasy world, where he will encounter friends, foes, and potential love interests who will help him discover this brand-new universe.

Please eke out a living in the parallel universe.