In August of 20XX, a portal to a parallel world, known as the "Gate," suddenly appeared in Ginza, Tokyo. Monsters and troops poured out of the portal, turning the shopping district into a bloody inferno. The Japan Ground-Self Defence Force immediately took action and pushed the fantasy creatures back to the "Gate." To facilitate negotiations and prepare for future fights, the JGSDF dispatched the Third Reconnaissance Team to the "Special Region" at the other side of the Gate. Youji Itami, a JSDF officer as well as a 33-year-old otaku, was appointed as the leader of the Team. Amid attacks from enemy troops the team visited a variety of places and learnt a lot about the local culture and geography. Thanks to their efforts in humanitarian relief, although with some difficulties they were gradually able to reach out to the locals. They even had a cute elf, a sorceress and a demig

High school sophomore Kusuo Saiki swore as a child that he would keep his psychic talents hidden, but his abilities still make his life difficult.

Defeating numerous villains in the abandoned area in Z-City but still having problems with rent money (and continued harassment from the landlady who says he's 3 months overdue), Saitama speaks with a shop owner who is being forced by a local gang to surrender his store's deed. Several other shops have gone out of business and his store is the last one; a conversation between the gang boss and one of his stooges reveal that the boss has had an impulse to buy out all the stores in the area to destroy them.