Demon Age: He Was Awarded Level-SSS Demon Talent at the Beginning

Leon traveled through the alien world. The dark era came.
Everyone got a special identity, demon, or law enforcer.
The mission of the law enforcer was to eliminate demons to increase his life span and strength.
Therefore, the law enforcer and demon were like natural enemies.
As a demon, Leon had reached the demon level of SSS.
As long as he killed the law enforcer, his skill would be limitless upgraded.
While the other demons were trying to avoid the law enforcers, Leon was looking forward to their arrival.
"You've killed 10 law enforcers. Congratulations on your successful up level to eternal demon king!"
"You've killed 100 law enforcers. Congratulations on your full-level skill, eternal life!"
Finally, Leon became the existence that all law enforcers were eager to avoid.
Leon: "Why didn't anyone come to kill me?"
Law enforcer: "You have killed all the people who came to kill you!"