GATE 0: Thus The JSDF Fought At Ginza

In the summer of 20XX, a "gate to another world" suddenly appeared in Ginza, Tokyo. What came pouring in from inside was a mysterious army and a group of hideous monsters. They go around slaughtering people, and Ginza in broad daylight quickly turns into a hellscape. While everyone was helplessly thrown into confusion in this state of emergency, there was one man who was brave enough to move around. That man was Youji Itami, an otaku Self-Defense Force officer who would later be called the "Hero of Nijubashi!" (Source: AlphaPolis, translated)

On a certain summer day in the year 20XX, in broad daylight a gate to another world appears in Ginza, Tokyo. An army and a swarm of monsters come storming through the gate. The Japan Ground Self-Defense Force is able to defeat the invaders and they head through the gate into uncharted lands. An epic fantasy about a battle between the human race and another world filled with dangerous enemies and beasts! *Source: Alpha Manga*