Challenge: The Grim Reaper comes to Issei at the moment of his death at the hands of Raynare. He is sick of having to deal with his job and rants on about some stuff (you can decide what that is) and decides that Issei should take his job. This can be any pairing you want it to be. As for how and what can do.
He can see dates above peoples head that indicate when they were born and when and how they die. Like this : February 12, 1994 - October 31 2014 Cause of death: Heart Attack
He can teleport in order to collect the soul of the decease to send them to the afterlife.
He will eventually be OP but he must first train to use the powers of the Grim Reaper. There will be a knowledge transfer on how to master them. However that does not mean he will know how to use then right off the bat. You can include somethings that are so easy he can do it off the bat but the more complicated shit will take time to do.
Also Asia must be the first soul Issei Reaps. Deaths until Asia's death will be handled by the scythe of the reaper since it will have a conscious. Male or Female you decide.
As for how the power got transfered. The Reaper Heaved up his scythe and brought it down on Issei's heart. With the Scythe implanted into his heart, he started a chant (Not good with that I'll leave that up to you)
Also Non-Perverted Issei, Darker Issei.
PM if you wish to take the challenge