In the far future, people live 1000 meters deep underground. Technology is abundant, but life is a constant struggle. An organization sought to end this by sending people back in time to recover lost natural resources. Elcia is one of those people. As a Time Negotiator, it's her job to travel across various dimensions and negotiate with people of the past. However, in a strange twist of fate, Elcia accidentally stumbled upon an unknown dimension known as "Area-X" during her very first mission. Following its discovery, more bizarre incidents and conspiracies awaited her one after another—all of this eventually led to discovering the uncanny nature of the world and how it all ties to Elcia's very own mysterious past...