Re:sleep - The sleep that puts you in another world

Jon had a dream that made him unable to distinguish between reality and dream. He went on an adventure in another world for three years in his dream. When Jon became accustomed to that world, he suddenly woke up and forgot all the events in his dream. When Jon fell asleep again, he continued the dream he had before, but his memory had been reset, as if Jon had never dreamt it all.