The Soldier and the Slave. The Alien Gun, #1

Ever since slavers took Ishiko as a child to be trained, she dreamed of the day she would be sold. She excelled at her lessons and became the most skilled and expensive slave in Master Wong's inventory. When her new owner walked into the room all her fantasies evaporated and her nightmares came to life. Master Flint came from another planet and stood taller than any man she ever saw. His size was intimidating, but what scared Ishiko most were his eyes, as cold and passionless as a corpse's. The off-worlder erupted with violence and moved with super human speed and precision.
With the blast of his gun, Ishiko found herself in possession of something she never expected to have: her freedom. This stranger came to set all the slaves free, but it was a wasted gift for Ishiko. She spent too long as a slave and knew she couldn't survive alone in the world outside. Besides, losing the slaves and having so many of his men killed put Master Wong in a precarious position with his enemies.
The only way to regain his standing was to capture his slaves and kill the man responsible for this insult. To keep her fragile freedom, Ishiko must flee with her new Master. It doesn't take long to discover Master Wong has an army of employees throughout the city. After a deadly encounter with Master Wong's men, Ishiko learns the source of Master Flint's speed and skill: Aliens from a lost civilization built his gun, but even the advanced weapon isn't enough to save them from Master Wong's rage. Master Flint's rescue turns into a race to his ship to get Ishiko forever beyond Master Wong's reach.
If they fail, Master Wong's revenge will have Ishiko begging for death days before he grants her the final release.