The Will of the Soul: Chasing Fates

Love conquers all that even the rule of life and death is no longer a barrier. What if death can bring one's life? And that one's life is changing their fates. How far back do their destinies cross between life and death?
An importunate Soul who can't accept she died jumped from a carriage heading to the purgatory journeys into the land as she accidentally possesses an agnostic Mortal, Trinity--she who does not have faith and doesn't care to her life. Thinking her life is useless without the one she doesn't even remember.
A Grim Reaper who wants to go through the light has no memory of his past life and wanders the earth without a name, tasked to guide the importunate Soul. God gave them a chance to go to heaven by having a mission.
But what if as he guides the importunate soul makes him recover his memories?
Under covering their past, while discovering their own fates.