• •
  The setting is modern-day Japan. In the world of humans, nations are recognized merely as "countries." However, in reality, each nation has a being called a "CountryHuman" who lives bearing that country's history, culture, and the memories of its people.

They are fundamentally forbidden from interfering in human society.

However—in Japan, there exists a "Boundary" where these national entities secretly gather.

Located deep beneath Tokyo, it is a place unrecorded on any map.

There, nations conduct diplomacy, exchange information, and occasionally handle incidents that must never be known to humanity.

Then, one night.

Japan suddenly vanishes from a part of everyone's memories.

Japan enters the living room where everyone is, as usual.