I like the idea of reliving others' lives to restore your own, but I didn't quite understand how the tasks were meant to be making your own rebirth more worthwhile -- they just seemed to be random fights thrown in for something to do, rather than actually having a purpose -- especially when you're asked to "slay the demon lord" and then... that character just ends? I assume that was how they died, but it would've made sense that you could then try to win the fight they lost and that was what made you stronger and able to be reborn?
The mapping could definitely do with some more variation and attention, rather than just big open squares with random enemies, especially since so many of the characters' lives seemed to be so repetitive. It would've been cool to see some scenes or dialogue with people in their lives in order to give each character a bit of depth to them, outside of their little job.
Again, I think it's a good premise, but it just feels more like the start of something that didn't quite get finished.