Death Countdown

In a world where parasitic entities from Hell run rampant among the human world, there's a group called the Exorcist Bureau who is tasked with defending humanity against the residents of Hell.
These parasites are commonly known as Akuma, and these beings feed off negative human emotions. The beings grant special abilities to their human hosts, who can use them at will. Many of those fused with Akuma join the Exorcist Bureau, but once an Akuma completely takes over the host's body, it's called an Akumai, and the Bureau takes steps to make sure the Akumai doesn't run rampant.
Akumai's only goal in taking control of their target is to feed on others, and their power grows with every victim. Because of the great threat Akumai pose, the Bureau created their own specialized unit called the Ex Hunters, specially trained Exorcists tasked with tracking Akumai and destroying them.
Levi Goldvein is the last of the main branch of the Goldvein family, a notorious family line known for producing powerful Exorcists. But rather than close combat or Spirit Weapons, Levi chose to become a Tamer.
However, unknown to all but himself, his Familiar was none other than the First-Rank Titled Grim Reaper, the strongest being in Hell other than Lucifer himself.
During one of Levi's freelance requests, something goes strangely wrong, and both Levi and his Reaper are confronted by the Exorcist Bureau. They're requested to join the Bureau's elite Squadron, the Ex Hunters, in order to combat the sudden increase of Akuma and Akumai.
The Reaper wanted to refuse, but followed Levi's decision, though she had a few conditions they had to keep. One: They must never know I am a Reaper. Two: They must never know the name from my past life. Three: Levi must never meet the Chief Exorcist.
These conditions confused Levi, and started raising questions that would have been better never answered. Who are you? How do you know the Exorcist Bureau? Why are you a Reaper?
Levi and his Familiar must continue down the path they chose, a winding, dark path full of lies, secrets, heartbreak, murder, and fragile, pure love.