Light Yagami hates himself. Not because he is a killer, no he could never hate himself for that, but because he killed the one person who would ever under stand him. He hates himself more than he has ever hated anyone or anything he has ever come across in his short pitiful life. He hates himself more than he hates criminals, more than he hates Misa for being so pathetic but so much more smart than he is because she has to be, to be able to manipulate him into doing what she wants. He hates himself more than he hates L. Oh and how he hated L. Hated him with such an obsessive burning force it was painful. He hates himself so much he wants to curl into himself and carve his insides out and just die.
He hates himself for killing L but at the same time is oh so proud. To be the one to beat L. The L. Who else can say that? Who else...
No one! No one else can say that and it makes him hate himself all the more. He can't look in the mirror because he hates what he sees there. A narcissistic, weak, disgusting human. Light is not stupid. He knows he is not a god. There is no way he is a god. He doesn't really want to be a god because he has seen them. Sick, twisted, grotesque. He doesn't want to become that but alas! He already has. And he knows, he knows what he has become and it sickens him. Makes him sick at night. When no one else but a laughing, always laughing, god can see. And look where this has landed him! Near thinks he as won but not really. Light was so far ahead of him he even orchestrated his own death. Told Mikami exactly what he was going to do and how it was to happen. Mikami ever faithful, followed his god to his own death! Near thinks he has won when Light runs away but it's not true. Light just refuses to die where such a horrible mockery of L is. Near doesn't deserve the title of L. He isn't worthy of such a title.
So Light runs. Runs to where he can die under the ever watchful eyes of a laughing god and L. Runs so that he is alone except for the two beings that are just so painfully real to him. It doesn't matter if one is only in his head. That doesn't make it any less real.