Ryuk, a shinigami from the Shinigami Realm, appears to be bored with the entire realm.
In school, Light is asked into translating a sentence into English which he did. While walking to school, Light hears a crime news. He and Ryuk have the same idea: they're bored.
In the next day after school, Light finds a notebook falling to the ground. He gets it to see that it is called Death Note and reads it to find a rule that if anyone's name is written will die. Light refuses to believe it and leaves it behind, but he gets it.
In his home, Light read the rules that a person must have that person's face in the mind in order for the Death Note to work, the death will happen in 40 seconds, the person will die of a heart attack if the cause of death is not written and details of the death should be written in the next 6 minutes and 40 seconds. Light thinks that the Death Note is a prank and lies down on his bed thinking about writing people's name and they die.
However, he begins to try it, but thinks that if he kills someone, he would become a murderer. Light has to find someone who is ok to kill, but no relation to him. Light turns on the news channel to see a criminal named Kurou Otoharada and writes his name down. He waits for 40 seconds and as it passed, nothing happens. Light thinks that the Death Note and expects that it didn't work. However, the reporter has revealed that Otoharada dies from a heart attack. Light thinks it's just a coincidence and his mother is calling to go to his cram school. Light plans to test the Death Note one more time.
At Gamou Prep Academy, he begins to think about killing Sudo, but he has to avoid killing people he knows off and start thinking if people will care if he disappears for one day. After school, Light encounters a criminal named Takuo Shibumaru and writes his name and the cause of death: traffic accident. Upon seeing the results, Light finds out the Death Note is a real object. Meanwhile, Ryuk goes to the human world to get the Death Note.
In 5 days later, Light goes to his room and laughs at all of the names he wrote in the Death Note. Ryuk is amazed that he likes it and Light screams. Ryuk introduces himself. Light shows Ryuk and tells him that he is prepared what will happen next. Light asks him if he's going to take his soul, but Ryuk replies that he is not going to do anything to him.
When Light's mother comes in, she can't see Ryuk and leaves. Light asks him why is he chosen, Ryuk replies that he didn't and that he told him that he's bored. Light replies that he is also bored because of crime. He plans to use the Death Note to become the god of his new world.