Three hundred and fifty years ago, a portal opened in Kansas City, Missouri. Monsters and beings unfathomable to the human mind came out and attacked the surrounding area. However, thanks to military intervention, the beings were killed, and the area around the portal was captured. The government set up a research and defense department to study the portal and defend against any monsters that may come out again. Eventually, people entered the portal and realized there was an entire world on the other side. These people were not human. Instead, they contained races such as elves, dwarves, beastfolk, and dragonkin. After seeing a poster asking for recruits to help study the human mind and body, Shinji was accepted into a new program to study the relationship between humans and these people to discover if they could co-exist. Although, no one told him the details first.