When/Where is Death Note Ascension set?

Death Note Ascension is set long after the events of the Death Note manga, not too far in the future, in an alternate present timeline. It's set within Tokyo itself, though primarily the Kanto region. That isn't to say that we won't expand to worldwide locations, however.

What's the main story?

The main story is that the Shinigami King intentionally churned out many copies of the Death Note (an idea inspired by Ryuk's escapade with Light) and had other Shinigami pass them onto the Humans. One of the wielders in particular has taken up the title of "Kira" and is referred to as the True Kira even by the Shinigami. At the same time, the police launch an investigation to capture the True Kira and the Kiras following him.

True Kira? What's his goals?

Nobody knows the True Kira's intentions, but they all know that he's looking for an apprentice, preferrable someone who shares his ideals of creating a new world. Whether or not the other Kiras comply with that view is a contested matter. The Death Note gives the wielder the power of the Shinigami and it's up to them how they use it.

What about L?

L's motives are clear-cut. He wants to stop Kira (all of them) as soon as possible. Enlisting the help of as many officers as he can (that are willing, of course), the Kira Task Force steadily grows and grows. However, the time will come when either Kira is caught and his reign ended, or Kira beats them at their own game.

Wait! I need some more info!

PM me what you want to know and I'll add it to this list.