A so-called time well uses gravity to create a nearly closed loop of space in the universe, causing an enormous difference between the flow of time inside and outside the well without accelerating anything close to the speed of light.
Inside the well, life cycles endlessly. Outside, only the blink of an eye passes.
Two twins grow up in the same environment, meet all the same people, experience all the same things, and make all the same choices. So are they two people, or one?
Perhaps this is where the story begins: the truth of being reborn.
The title may be clichéd, but the sci-fi is absolutely hardcore.