Light Yagami is an ordinary university student. One day, he receives a death note which changes his life. The death note awakens his warped sense of justice and genius. He becomes murderer Kira and punishes criminals. L is a well known private detective. L appears in front of Light Yagami. L defines Kira as evil and decides to catch Kira. Then N, who has a beautiful appearance but dangerous existence, appears.
There are numerous votes stating "No" as many are voting on this page in assumption that it's for the 2006 anime series rather than the 2015 live-action adaption- but yes, in the final episode of the series a character is shown burning to death and another narrowly survives the same fate.
There are shinigami (gods of death). They aren't ghosts exactly, but they "haunt" a human and only that human will be able to see them in normal conditions.