I took care of him, but he came back obsessed with me

I possessed the body of 'Cersinia', the only sorceress in the Empire who can conjure the power of fire.
Fortunately for me, I still had three years before the original story began.
Determined to change my fate, I decided to visit a gambling house, where I hit the jackpot. But Instead of money, I was offered a young slave boy as collateral.
"Regarding your name, what about Ben?"
"I like it. Ben… it sounds good. Thank you…."
As I took care of the poor boy, I started to grow fond of him.
In a world with no one to turn to, I thought that I had finally met someone I could rely on, but…
One day, the man who had agreed to remain by my side disappeared without a word.