Myth is a story of archetypical personas who behave in ways and with motives that we recognize in ourselves. We use myth as a way of reminding ourselves of the relationship between motives, actions, and consequences. Myths can serve either as inspirational or cautionary tales, and sometimes as both. But “myth” can also mean a fabricated story intended to create a false impression, and to achieve storytellers’ ends when they have decided the truth will not suffice. We apply the myth of Cassandra to the millennium-long recorded history of giant tsunamis in Japan. After each of these catastrophes, survivors sought to warn future generations of their recurrences. But, each time, their progeny eventually lost the memory of these lessons, and lost their lives when the next monster wave overwhelmed them. Only when they kept the lessons as living knowledge in everyday life, could they manage to escape from monster tsunamis. In this chapter, we use the myth of Cassandra in conjunction with the myth of Prometheus, the bringer of fire to humankind, as a metaphor for Japan’s growing reliance on nuclear power. Government and utility companies built powerful but inherently dangerous cauldrons in the nation’s disaster-prone landscapes, assuring the public they could control the fire’s fury and defend it against nature’s. As images of atomic bomb victims were still vivid and widely shared in Japan, they had to overcome the public fear of radioactivity by fabricating a “myth of safety.” The nuclear disaster made the public distrust the government and utility companies, which lingers in the process of reconstruction from the disaster. Myths can either reveal hidden truths or mask hidden lies. The Japanese people must now learn to distinguish one from the other.