At 15:07 on February 11, 2025, the "Nankai Trough Mega-Earthquake" occurs. At that time, the protagonist, Saito Mei, who was at Nagoya Port, sees the city completely changed. As a "major tsunami warning" is issued, Mei tries to escape to safe high ground. However, next to her is an "elderly person who is injured and unable to move"... Will she abandon him or help him? She is forced to make the ultimate decision. And the fear of an "invisible tsunami" that will strike. An unprecedented disaster that will surely occur someday. What will happen when that happens? How can we survive? Based on thorough research, this is the "reality of an earthquake that will occur someday."