Gate: Jieitai Kanochi nite, Kaku Tatakaeri – Enryuu-hen

A doorway from another dimension forms in the present-day Ginza neighborhood of Tokyo, opening the way for an army of monsters and Roman-styled medieval troops to invade the city. The Japan Self-Defense Forces successfully resist the enemy with contemporary weapons and strategies, and they cross through the Gate to set up a forward operating base and begin peace talks with the Empire from the other world. However, other countries seek to use the Tokuchi for their own reasons and are envious of Japan's unique access to the Gate. Additionally, their government, which is wary of further meddling in the affairs of the Special Region due to public backlash, keeps a careful eye on the JSDF's activities. A reserve JSDF officer named Yji Itami is dispatched to study the other world, where magic, dragons, and elves are real. He will use his familiarity with fantasy literature to navigate this unfamiliar environment. During his exploration of the Special Region, he ends up sacrificing himself to save its residents, including Imperial Princess Pia Co Lada, from an ancient dragon and a group of marauders, opening the door for negotiations and placing him in the company of several local girls who have grown fond of him. The Imperial Crown Prince Zorzal, however, resolves to make Japan pay in blood by taking control as a dictator and prepares for all-out war after he humiliates him in order to free a Japanese prisoner from his grasp. Thus, in order to maintain the status quo and bring about a peaceful resolution to negotiations with Zorzal's father, Molt Sol Augustus, the JSDF is ultimately compelled to engage in violent war action.