The Burdens of the Lost
Souls. The soul is a magical incarnation of the human body. If those souls were to get reincarnated those souls will be reborn into an identical version of themselves. The souls of the unworthy get sent to Hell. The worthy get sent to Heaven. Sometimes there are anomalies where the unworthy can reemerge to redeem themselves of the bad deeds they've done. Other times, the worthy fall out of the heavens and get sent to Purgatory. In order to receive the blessing of Rebirth, you have to show you are ready for a redemption. Fallen Angels or Ascended Demons can have a chance at Rebirth when an angel or one of the Seven Deadly Sins comes to them with a task. As Akumo Arino and Tenshi Katria are both assigned with the same task, it is their job together to stop the magical incarnation of the unstable hierarchy known as The Anomaly.
The world-building is really interesting, and I enjoy having a mixture of heaven/hell/purgatory along with traditional Biblical demons and powers. The characters are introduced quite rapidly and there's a lot of "telling" the reader about events, rather than showing it through the lens of the character's eyes. Otherwise, there's a very solid concept here, and I think the author has excellent potential, especially with their world-building skills!