As a student, he was friends with a woman from Germany. Now Yoshiro is very old and imagines calling her to ask if her grandchildren and great-grandchildren are healthy, what they eat, and whether the environment in Germany has changed like it has in Japan. He envisions visiting Hildegard and traveling to Europe once. After a catastrophe, Japan has severed all connections to the outside world. Yoshiro takes care of his grandson Mumei. The children born from the catastrophe are weak and sickly, but at the same time, they are already old and wise, cheerful and a glimmer of hope. Mumei is free from self-pity and pessimism. As daily life in Tokyo becomes increasingly difficult, a secret organization is trying to find a cure for the children of the catastrophe, with Mumei involved. The novel is set against the backdrop of the so-called triple disaster.