Hereafter

What if you are given an ability to enter someones body while retaining that persons memory? What would you do? Ruin that "persons" life? Change his/her way of living? Corrupt its soul? Etc... now that you are that "person" you have the choice on what you will do in that persons life. Without knowing its consequence would you still continue to use this "power"?. Will the person you possess will retain your memory? This is a story of a guy who obtain that powers in exchange of his precious memories. What our main character will do when he found out that every time he uses this "powers" will eat a memory.