When I watched episode 25 of Death Note (AKA the one when L, Watari, and Rem died), I noticed that Light was strangely kind to L. Is that because he was nice to L before he died, or because he actually thought of L as a friend? This is something I have been pondering over ever since L said that Light was his only friend.
This might be my personal opinion, but this does not look like the face that a person would show his friend when that friend is dying. Light had been pretending to be L's friend for a while, so by (over-)reacting he achieved two things. The first would be keeping his image and the second would be giving him a reason to go looking for the Death Note, that he knew would be laying around somewhere.
In the Chapter 32 (Vol. 4), Light was thinking if he should kill L or not, and then Ryuk said he thought that Light's doubt was because L called him his friend. Then Light answered that on the outside, Ryuuga/L is his friend, but actually L is Kira's enemy. And in various other pages, you see Light thinking about "killing L" - hardly a thing a friend would do. So, no, Light (at least with the memories of being Kira) doesn't consider L truly a friend, it's just part of his acting.
I do believe so yes. Light (that being the Light who didn't realize he was Kira), did like L and considered him a friend. But Kira (that being, the Light who has Kira's memories) considered L his enemy.
What is interesting and what I feel is not really considered by fans, is that Light and Kira are the same person.
Light without his memories, is STILL Kira. Kira WITH his memories, is STILL Light.
What I mean is, just like how Misa would still remember her feelings for Light even while losing her memory, likewise, I do believe Light would still remember considering L a friend during their investigation together (after he'd lost his memories).
His Kira self is more dominant, but based on how Light was seeing L when he looks at the empty chair, and laments on how things aren't interesting without L, and even cut scenes to Light's blank looking face when he's on a date with Misa right after his lamenting about L being gone, it gives off the idea that Light, somewhere deep down, misses L.
He misses the challenge, he misses his "friend." Even though L was Kira's enemy, Ryuuzaki was Light's friend. They had much in common, they were equals, literally no one could match up to them the way they did to each other, so no matter what, Light found something unique in his relationship with L. I do not believe he never cared at all.
It's just that he cared about being God of the New World far more, and thus was willing to throw away everything else for it.
There are many animes I have come across that have characters with split personalities. I think this is the case with Light. I believe Light is not truly evil, but his other persona (Kira) is. I think this is also the case for Light and L's relationship. Light does consider L as a friend whereas Kira sees L as his enemy. Although many fans think Light acted a lot, I think there were plenty of moments where Light and Kira were in conflict inside Light. As I read elsewhere, If Light had never found the death-note and became Kira, he would have become a detective alongside L and the two would be friends. I've also come across many scenes where Light seems to miss L.
When L confessed He thought of light as a friend I think on a conscious level it was simply a ploy, but there actually was some kindling of empathy. Also even though L admitted, ‘I think I wanted you to be Kira’ When he died he had a wide eyed expression seeing Light smile as if he had just been betrayed. As for Light, he never seemed to portray much kinship for L. Nevertheless I think it would be wrong to assume he hated Light. In episode 36 near is wearing a mask of L, and you can hear Light thinking of how it is dishonouring L, which is really strange considering Light plotted his death. I don’t think L and Light were really friends, but subconsciously I think they both knew that under different circumstances they could’ve been, and I think that shone through when Light first brought L in from the rain. Also in lights last moments when he’s dying, he sees L. You’d expect him to see his dad as when people pass, they tend to have visions of those they have loved who have passed away. Instead he sees L, I think he really did care for him.