Shooting discipline

In the world of obius, there is a profession called gun fighter. It is said that in ancient times, there was an alien invasion. In order to resist the powerful invaders, the most powerful of the gun fighters, a generation of gun king, led many gun gods to successfully repel the invaders, and exhausted 90% of his accomplishments to seal the space-time crack. Since then, the gun King disappeared in the world and disappeared from there but after 10000 years, the space-time crack shook inexplicably, but no one found it