Akira is The Antichrist.
Devilman Grimoire is the latest incarnation of the Devilman universe.The Devilman universe has gone through many cosmic reboots. First was the world of the original Devilman manga. After it was destroyed, it was rebooted into the world of Violence Jack. This was then rebooted into the world of Devilman Lady. This was then followed by the world of Shin Violence Jack. And then it was rebooted yet again, this time into the world of Devilman Grimoire, which seems to combine elements of all the previous incarnations (so far featuring characters from both the original manga as well as Devilman Lady) as well as elements from the 1970s anime series. In this sense it is similar to Stephen King's The Dark Tower series, where time also works in a cyclical pattern. The fact that Grimoire is set in the present day, with characters who originally existed in the 1970s (Devilman) or early 2000s (Devilman Lady), also bears a resemblance to the History Monks of Discworld and how history is manipulated by them.