Little Transmigrator: Holding On To The Big Shots

The innocent and naive Ciara Smith passed through a lot of mishaps while alive. Breathing her last breath, she came across a Soul Reaper, who informed her of her gift from the heavens, the gift of Transmigration, with him living in the void if her mind. His Master, watching their every movement.
But, she could only be given this gift when she completes a task, which is to be reborn and to change her fate.
Failure to change her fate, her soul would perish. But if she does, and lives her lifetime, she would be granted the gift of being a Transmigrator, with the Soul Reaper, Alexander,  in the void of her mind.
After transmigrating, failure to fufil her mission, both her soul and the Soul Reaper would perish,and another Transmigrator would be chosen. 
Reaper: You're already so strong, why are you still holding down the big shots?
Ciara: You don't expect me to let go of such beautiful master piece, do you? Just look at them. I'm sure the previous owner would be glad to know I let such master piece land on her doorstep. Just wonder how happy her soul would be.
Reaper: We both know this has nothing to do with the previous owners. You're just so hungry for men
*He rolled his eyes*
Ciara: Yeah, yeah. Whatever. I'm gonna enjoy my missions either way!
Transmigrating into various lives, Ciara would be given the back story about the owner of the body she would possess as well as how the owner passed away, before being reborn as the owner to exert revenge.
Join Ciara and Alexandra as they journey through worlds, living different lives and maybe, also searching for love?
Who is Alexander's Master and why exactly did he choose Ciara, of all the souls to have been lost due to various mishaps?