ゲート0 -zero- 自衛隊 銀座にて、斯く戦えり

Youji Itami is off duty and walking to a doujinshi event in Ginza when a stone gate opens in the middle of the district and an army in Roman-style armour comes through it with dragons and monsters behind them. He falls back on his Self-Defense Force training, steers civilians toward the palace grounds and ends the day known as the hero of Nijubashi. Takumi Yanai wrote this novel as a prequel, expanding an attack the main Gate books cover in a few pages.