In case you don't know about the series, I just read all 12 volumes of the manga and can summarize it for you. The person in the video is Light Yagami, the hero, and he was out to make the world a better place. He reduced crime by 70% all across the globe. He was a great man who sacrificed everything in the name of justice before he was felled by a bunch of short-sighted, morally bankrupt fools.
It was a very sad, tragic ending. Although Part 2 wasn't nearly as bad as I had been told. True, Near was no L but a lot of L's time was spent in the boring Memory/Yotsuba Arc so that didn't help. The beginning is the best part of Death Note, when Light was first creating his ideal world.
P.S.
Light x Misa forever. At least they are together in death....