Guest appears suddenly during a War Game and may belong to any faction.

This is a fantasy story set in an alternate world where war serves as a diplomatic tool in the form of a sporting event with no casualties. The protagonist is a boy summoned from modern-day 2011 by an otherworldly princess to be a Hero. War in this world is depicted as an attraction reminiscent of field athletics. While the competition involves interference and counterattacks using weapons like swords and special moves, and features superhuman battles between characters, anyone hit by a shell or a high-powered special move is merely incapacitated for a while. It is portrayed as a "war-like game" where no one dies or gets injured. Consequently, there are almost no lethal or violent expressions. Furthermore, there are almost no scenes showing the dark side of humanity or negative elements. Due to this setting, the negative issues that usually arise from depicting conflict are avoided, resulting in a story where no villains appear and everyone is portrayed positively.