Yagi Takeru has been residing in the Touma family household since losing his parents. He was raised by Touma Rokunosuke, the master of the house. His daily life is filled with companions such as Yamato Takeshi, his best friend and rival from the kendo club, the Shiratori sisters Kotono and Asuka, and his childhood friend Oosu Seri. Everything is peaceful until one day an earthquake hits the school and changes everything. Takeru wakes up to find the school looks like it has been deserted for centuries and has crumbled into ruins. He also realizes that all the teachers and students have vanished. He meets up with Seri and Asuka, and they escape from the ruins, only to discover that the town where they used to live is completely vacant. Then, figures draped in cloaks appear before him. They are informed that they have been brought to another world.