From There to Here, From Then to Now

This is a reincarnation story, but in the reverse direction.The main character is a hero destined to save the human kingdom and end the human-demon war. Along with his party, he confronts the demon king.He defeated the demon king, but at the cost of many lives, including his.The hero died.And then he was reincarnated in another world.A world without swords and magic called Earth......Or is it really the case?