It's time to bring a gun to a swordfight.

In 2005, inter-dimensional portals appeared around the world. Millions of people lost their lives by hordes of ferocious beast. Every nation retaliated. In a short time, the armed forces managed to eradicate every single monster on earth.

The modern military had overpowered the beast. Human civilization completely changed afterwards. The monsters that were once a disaster became humanity's new resources. Sadly, the armed forces got nothing after they saved humanity. Walker was the one who took the credit. They were a handful of humans who had been chosen by the gods.

Walker was equipped with magic and superhuman abilities by the system. They could pass through the portal and hunt monsters in Ethereal. Aware of their power, they stepped out of line. Walker became the new ruler. They were free to colonize, kill, and enslave the world behind the portal. Ethereal dwellers were helpless. Their civilization declined. In the end, the Kingdom of Valora, a land of the long-lived race, sent their crown prince to Earth.

He rebuilt his kingdom with his experience as a special force operator.