Majin no Umi is a story of Ainu revolt in 1789. At that time Hokkaido was under the control of Japanese government (Bakufu). The Ainu in Kunashir and Menash had a revolt to be free from Japanese exploitation and oppression. This book is the masterpiece of Maekawa Yasuo (1921 - 2002), together with his former work Yan (Kôdansha, 1967).
  Tsukinoeaino, leader of Toputo Village on Kunashiri Island, made it a rule to fight against any foreigner who tries to take Kunashiri Island. When he knows the power of Japanese government, however, he begins to trade with Japanese in order to improve the life of village people. But the Japanese traders from Ezo (now Hokkaido) severely drive Ainu people with a little amount of rice or sake. Setsuhaya, son of Tsukinoeaino, is against his father, and trys to make his own village in the mountains. His followers are taken away during his absence. Setsuhaya and other young Ainu men attack the office of the Japanese. Ainu at Menashi in Ezo also rise against Japanese. When Tsukinoeaino comes back from hunting, he knows of this revolt, and persuade his son to surrender. Setsuhaya follows his advice in order to save the people of Kunashiri Island. Bukitemaaino, a Japanese who once cured Setsuhaya's wound, hurriedly comes with the paper to discharge Setsuhaya and his followers, but the execution has already been carried out.
  Maekawa went to China in 1943 as a student soldier, and came back to Japan in 1946. When he was in a puppet theatre company in Hokkaido, he saw Kunashiri Island from Nemuro, and he had strong wonder and anger "why people hate each other." This anger made him write this book. In this book, Japanese are not simply 'bad,' or Ainu are simply 'good.' Bukitemaaino, a Japanese, said that he was a human, not a Japanese or an Ainu villager. Setsuhaya loved Shianu, a girl born at Ainu and Japanese parents. A Japanese swordsman also showed sympathy to Ainu. This attitude of the author gives reality to the story. Illustrations by Toko Nuburi have warmth as well as strength, and help the reader imagine the Ainu world.
  Majin no Umi received the Japanese Association of Writers for Children Prize in 1970.