Gate

A gate opens in Japan. A magical/fantastical medieval army comes through and attacks. Japan forces them to retreat then sends their armies through the gate to their realm, fighting to occupy the gate's area. Itami's team is sent to learn about this realm and their people's culture and assimilate to help resolve this conflict peacefully. This realm's king seeks to manipulate Japan into defeating his enemies. Itami's team must gain the aid of a mage, elf, and demigod. Mythical creatures interrupt.