Kanda doesn't love Lavi. He doesn't love him when Lavi calls him by his first name and acts all together too familiar with him. He doesn't love the smile on Lavi's face that belongs to everybody and nobody. Kanda most certainly doesn't love the look that rarely passes over Lavi's faces and proves that he isn't as much of an idiot as he pretends to be.
Lavi doesn't love Kanda. He doesn't love that psychotic gleam in the other man's eyes as he threatens a painful death to anybody who angers him, namely Lavi. He doesn't love him while the Bookman watches Lavi entirely too closely to ensure he isn't forming any emotion bounds. Lavi most certainly doesn't love him when he comes back from a fight with his wounds closing even as he walks to the infirmary.
But Kanda thinks that maybe, just maybe, that when the timid morning light catches Lavi's bright red hair and makes it glow and his lips are curved up in a small honest smile that he could be convinced that he loves the idiot. And Lavi knows that if somebody asked him while he was watching Kanda sleep with moonlight daring to stroke the long dark hair that falls loose around his pale face untroubled by emotion that he would tell them that he loves the manic.