Ryu Fujiwara wants to become an architect. Despite his looks, he is very considerate of others. While working as a part-time teacher, he gets acquainted with Kaori Ayase, who is a manager for the construction of a government official building, and they have a talk about architecture. He gradually becomes interested in her. The day before a tea party to convey his feelings for her, a large hole opens in the heart of the Earth. The total area of ​​the world is covered by water, and it is said that the surface is not suitable for life. Earth is over. But there is one continent left, which is the core of the earth and it is said that life exists there. People who survived on the surface, led by Japan, leave the floating debris, heading for the core of the earth.