GATE: Thus The JSDF Fought There!

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 demigoddess in their circle of new friends. On the other hand, the major powers outside the Gate such as the United States,China and Russia were extremely interested in the abundant resources available in the Special Region. They began to exert diplomatic pressure over Japan. A suddenly appearing portal to an unknown world—to the major powers it may be no more than a mere asset for toppling the international order. But to our protagonists it is an invaluable opportunity to broaden knowledge, friendship, and ultimately their perspective towards the world. (Source: Baka-Tsuki)

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*

A spin-off focusing on Princess Pinya's (from "Gate - Thus the JSDF Fought There!") life before the "Gate" opening to the other world event.

A 4-koma set in the "school" at the Alnus base.

After graduating from their constant fighting, some magical girls were unable to keep up in class, got poor grades, and became NEETs. In order to help these poor former magical girls, the cleaning company "Mei Company" was founded! Will swapping their magical staffs for cleaning tools help to rehabilitate them? Gate protagonist Itami's beloved doujin manga about former magical girls cleaning up messes.

A spin-off of Gate: Jieitai Kanochi nite, Kaku Tatakaeri series featuring three main heroines as up-and-coming idols and Itami as their manager in a world without war.