Sacrifice

Byeong, an 8th grader in a private school in Korea is given a chance to get his dead twin back. He finds out that changing the past could be dangerous. The boy that gave him the chance goes back and makes the ultimate sacrifice to save Byeong's brother, knowing that he will see Byeong and Yeong again, but it will a different version of themselves. At the end of the story you come to find that the boy that went back in time had written it as a story, but you're not sure what was real and what was fiction.