L knew.
From the second he saw Light's picture, so smug and sure, yet hidden under a quiet, innocent confidence, L knew. He knew it when he sat behind Light in that class, he knew it when they stood side by side behind the podium—L the shadowed, awkward figure. Eyes too big and hair too wild, and his posture was even more exaggerated than usual.—Light, the boy who stood with an almost-lifted chin, eyes keen and calm and watchful. The humble one, the valedictorian, the brilliant acting.
L knew it more strongly, then.
And when they spoke, it was something smooth and non-forced, masking the immediate battle. The paranoia, the accusations, the hatred. Smiles that masked curses and L's hands were always in his pockets. Easier to avoid pointing a finger.
He knew from the way Light stood to the way he spoke, to the way he sipped his tea. Prim and carefully, as though posing for an audience of judging onlookers who would immediately dub him acceptable or suspicious. Light subdued the intelligence in his eyes, met just the proper amount of socialization requirements without appearing bored or annoyed.
L knew it when Kira knew him. In those quiet moments between the two where L would watch his screen with one eye and Kira with the other, where Light would stare idly at case files or some other insignificant thing. L would glance up in a casual way, and he would catch just the end bit of Light's staring, that thing that lasted no more than a second, but placed sharp pins on the back of his neck.
They washed, they slept, they ate. They shared ideas and argued over minor, unimportant details. Light, it turns out, was a very heavy sleeper. Something that L found impressive, given the amount of suspicion placed upon him. He would breathe deep and slow, he would sink deeper into the blankets, and L knew.
What he did not have was evidence beyond the circumstantial.
Even less so when that crack appeared. That long, jagged thing that split between what he knew and what he saw. It made Light's eyes too honest, his convictions when he spoke too innocent. It softened the position of his bottom lip and took the tension out of his right index. It worked its way over something so hard and so sure; it turned everything that L knew upside down. Buried it, even.
Light no longer found it necessary to keep constant eye-contact when they spoke. He glanced around at times with his words—eyes shifting left to access memory, right when he was creating something new. A hypothesis, something that his mind weaved from given facts. Left, right, left—and Light's laugher was genuine, then. Showing respect for his father and courtesy of the other members of the Task Force did not make him touch the pad of his right pinky finger against the middle of his palm every eighteen seconds for no more than a fraction of a moment.
There were certain elements that L knew to be present in Light Yagami that simply ceased to exist.
Out of this grew something new, something only mildly interesting and altogether unspectacular. It was glancing beneath that kept L interested. Light was drab, his words were drab, his demeanor expressed absolutely nothing of interest. His intelligence remained impressive; he never ceased to be an exceptionally bright individual. But that something was gone, the one that reflected L's own taunt against him ceaselessly.
Try to kill me.
And it is when L would become so incredibly bored that he would employ brutal methods to regain that aspect of Light. He would taunt, he would threaten, and when Light seemed just about to snap—a human can only be pushed so far—when his jaw was trembling with anger, when his eyes played the victim so well—that L would resort to the physical: grab the boy by the collar, make the space between them non-existent. Intimidate and prod until they it all devolved into a purely physical altercation, one that would leave bruises on both of them and end the life of a vase or two.
The accusations did not make this new Light Yagami want to brush it off airily and accuse L of lazy investigation. They upset him, they offended him, but beneath it all: they terrified him.
Light did not sleep so deeply, then. As a matter of fact, L found him to be a constantly annoying bedmate during those small times when he, himself, found sleep necessary. The younger tossed and muttered, gripped his blankets and lost his breath at times. This, L would watch, resting his upper body weight on an elbow, legs stretched out straight over the mattress. He would watch Light's brows furrow, watch the sweat bead just above his temple. Always intriguing, never revealing.
When L lost his own direction, resolved to moping quietly and following other leads with absolutely no interest—that, too, was genuine. Light Yagami was Kira, Light Yagami was Kira—but in that second, in those weeks, Light Yagami was an officer's son, top of his class, an innocent, determined boy being accused of mass murder. Light Yagami was not worth more than a second's investigation.
Amane was the missing link. L would prod and prod, and Light simply could not remember. He knew how Amane came into his acquaintance, but he did not know why. Light could not remember why he was guiding the proven Second Kira around as his girlfriend. He could not explain why her criminal status did not make him uneasy, nor why she would cling to him the way she did.
And yet, Amane was useless.
All L had were those small moments—the ones in which Light would suddenly go quiet for a few seconds, when he would become angry enough as the result of L's threats to rashly state that Kira wouldn't tolerate being mistreated by L, of all people. That something that made L's breath stop in his chest, made his head tilt just the slightest—nothing too noticeable—made him press his thumb to his bottom lip with a barely audible hum.
He hungered for those moments. They returned the spark, the reason, and L wanted to put Kira to death even more, each time they occurred.
"I want you to choke me, Light-kun."
"What? Ryuuzaki, don't joke about things like that."
"Only for a moment. You may stop before it causes harm."
"Why?"
"Because Kira would not stop."
Ridiculous and overly risky, and perhaps Light was under the impression that L was a madman.
Light refused; Light claimed that L was being overly dramatic, that his reason was based on nothing more than L's refusal to accept that he had not yet captured Kira.
And perhaps he was correct.
Perhaps.