You're a soul reaper. You travel between bubbles that fall through Purgatory. These bubbles are the possible final moments of people's lives, and you can either help them or ignore them. In the end, you need a soul to get to the next Bubble, otherwise you have to brave Purgatory, an infinite black void full of gargantuan, terrifying spirits that consume the bubbles once someone dies.
It's an interesting concept that allows you to spin a lot of beautiful, small stories. Stories of hope, dreams, loss, terror, love.... Lots of freedom. But there needs to be a reason that you eventually start to explore Purgatory ....