In the first chapter of Death Note two very different locations are set up, the Shinigami Realm in which the Gods of Death reside, and the Human Realm in which the main story takes place with Light Yagami in Japan. Ryuuk the Shinigami goes to the human world to look for his Death Note after supposedly 'dropping' it there. The Death Note is found by a high school student named Light Yagami. The Death Note is a supernatural notebook owned by Shinigami that has a lot of rules but ultimately will kill anyone whose name is written in it. Sceptical at first, Light Yagami tested the notebooks powers out of curiosity, and to his surprise, it worked. With his new God-like powers, Light decided to use them to exact his own brand of justice by killing criminals through heart attacks in the hope that people would realise someone is doing it and rejoice whereas criminals would live in fear. Ryuuk met Light and after they conversed he decided to stay with him, not as his partner or to aid him in anyway, but as an entertained spectator. At the end of the chapter, the police are in debate over the recent events, and a mysterious figure is introduced claiming this is a case he cannot pass up.
The overall theme of Death Note is morality; and in the way of justice the lines can be so blurred. Light Yagami is a straight A student and a respectable member of society. His initial intentions are innocent; in his eyes he is cleaning up the world and making it a better place by removing all of the villainy from it. Lights actions are something I believe most people of this generation would do if given the opportunity. The dilemma is, humans should not have authority over each others lives, in the end it is still murder regardless of intention, just like robbing a bank to support your family is still stealing, and that is why the police take it upon their selves to catch him. Feeling guilty about his first two kills, Light has an epiphany in which he concludes he has to carry on because he is the only one who could and would do what he's doing, narcissistic tendencies and a fixed perception of justice convinced him it was his personal responsibility to remove the world of evil and eventually, to furthermore, be worshiped as a God of the new world.
After a few days of Lights righteous movement with the death note, he meets Ryuuk, who flies in much to Lights surprise. Fearful at first, Light quickly regains composure and converses with the Shinigami; this says a lot about Lights character as he is at heart, human, and not invulnerable to human instinct, but then for him to be able to stare a God of Death in the face and confidently retort with him without any following sings of fear reflects a much darker, less human presence. It is in this first meeting that Ryuuk informs Light of the special bond the two share now that he is ownership of the death note; the Human realm and the Shinigami Realm have crossed over and only the people who have touched his death note can see Ryuuk. In character with his self righteous mind set, Light asked why he was chosen by Ryuuk, to which Ryuuk laughed at and assured the fool that it was only by chance that he happened to pick it up. The two then explained their motives to each other and it became fated that the two "Gods" lives would be intertwined, one for mere entertainment, and one for justice.