"Lovely Hated Hindrance"
Light Yagami was Kira. L suspected this and knew this subconsciously. Obviously Light was aware of this with L's tests, observations, and calling him Kira daily like a nickname which was said with a hint of amusement underneath along with seriousness. Naturally Light would put on a face like he always did before he became Kira and attempt to divert the suspicion away whilst defending his self. While most others in the investigation team believed him, especially since he was the son of the police captain and such, L and certain others continued to suspect him and kept an eye on him at all times. They had surveillance cameras, they had the police, they had the long handcuffs, and they had L. L was everything. Everything that could have stirred up his interest… and he did. He was intelligent, unordinary, a mask, justice, an enemy and first friend to clash against.
Keep your enemies closer to your heart, they say.
Light did exactly that, while still lying to his friend. A friend… could he really call L such a significant title? After all they were enemies, in which L hindered him from making the world a better place to live.
How and when he became his first friend while also still being his enemy and obstacle in his path is a question that he wasn't entirely sure of for once. It could be said that the world, fate or even god was cruel to do this, making friends fight against each other from separate sides. But that sort of thing occurs plenty of times in stories and undoubtedly, reality. Friends fight over something, friends fighting against each other in war, childhood friends finding each other in opposite sides in which both want to extinguish the other… and an unlikely pair becoming friends, each against the other's beliefs or something else. Their different beliefs… Like them. It's so much like them… it's atrocious.
Life with the Death Note is meant to be easier, as an unnatural, deceiving tool which allowed the possibility for the removal of criminals and other people who were in the way (L…) of a perfect world. But for them, Light and L, to be friends…
It made their lives more complicated and difficult than it needed to be.
But then again, life is unfair.
As was decided from the beginning and will be continued…
L was a hindrance.
(And he cared for him)
So he needed to remove him out of the way.