On July 25, 2017, at Haneda International Airport, KÅjirÅ and Shun, who are now negotiators working for the Ministry of Foreign Affairs, board a flight for a business trip. A mysteriously massive cube then materializes and swallows the plane full of passengers preparing for takeoff, including KÅjirÅ and Shun. In Kasumigaseki, Ritsu Natsume, who is working for the Cabinet Secretariat, researches news about the cube before receiving an email that KÅjirÅ and Shun were onboard the missing plane...