This is the story of a teenage girl, Cassie Smith, who, after her death, was recruited into Universal Mercenary Company. Something akin to a 'Rent A Hero Service', this mercenary company is one which offers its services to deities, devils, and basically anyone who can afford their service fee.

To put it simply, they commit the acts which the gods or devils can't afford to be bothered with doing themselves. Stopping apocalypses, getting rid of universal troublemakers, killing extremely overpowered, non-affiliated of course, demi-gods, etc. Sometimes, they are even tasked with ensuring that a planet falls apart or that chaos ensues; naturally, to them, it is just another job. If the paycheck is big enough, anything is possible.

This story is about how Cassie goes about coming to terms with her new job, serving as a supernatural mercenary for the first time, to be exact. Her first assignment, after going through 10 years of training, was quite simple. Assassinate a few big name officials. Be it Presidents, Mayors, Governors, Senators, Generals, etc. It did not matter, she just had to kill them and get away with it. Next was killing off a few of the Planet's Demon Lords. Naturally, those would be much more challenging in terms of elimination. Lastly, she just needed to make a name for herself in any way shape or form. Going down the line of a hero, or going down the line of a villain. It was up to her to decide whether she wanted to become this world's saving grace or become this world's worst nightmare.

With those few select objectives assigned to her, she was launched into this Fantasy like world. All she had at her disposal was a biological assistant A.I., a high potential in Shadow Magic, and an itchy trigger finger.

This is the story of this mercenary's first time in another world.