Jiro Kuwata SF Short Masterpiece Collection: Nightmare Messenger

One day, Ryohei, who hates school, gets into a fight with a bully and is thrown into a swamp. He survives, but that night he has a dream in which he kills those who harassed him. The next day, they were dead in reality. Are his nightmare just dreams, or are they reality? Eight stories of suspense, originally published between 1969 and 1980.