Disclaimer: I don't own Death Note, or make any money from this fanfic
A/N: This is a prompt fic from the Death Note Kink meme on Livejournal. The prompt was: "Light maliciously slows down L's metabolism, at first to lower his confidence and make him lose, but then Light ends up liking it."
Pairing: L/Light, though it's not very romantic.
Rated M for non-explicit sexual content
After only one month at To-oh University, Light was already pretty famous on campus. And not just for getting a perfect score in all subjects on the entrance exam, or for the epic tennis match with Ryuga. No, Light had managed to become an unofficial research project consultant for grad students. No project was without problems, and sometimes when hitting a roadblock, or encountering a minor setback, it was useful to get a second opinion. They would bring him the relevant literature, buy him a cup of coffee or tea, and wait for the genius to provide some much needed insight. He would read over the articles, make notes, ask questions and give his opinion. And he was so polite and helpful that they would often buy him gifts to thank him for his time.
Best of all, this was an area where Light could easily beat L, thanks to his social intelligence. Two weeks ago a hapless grad student had decided to try asking the other student who had received a perfect score on the entrance exam for advice. Bad idea. After five minutes, Yoshiaki was dryly informed that if he was having trouble isolating the chemicals in recruitment pheromones for Vespa mandarinia japonica, perhaps he should re-take introductory organic chemistry. Word spread, and L hadn't been consulted again. Light smirked inwardly at the thought. For all his intelligence L had very little tact. A fact which made it all the more satisfying to excel in an area where L had failed. True, his time could be better spent judging criminals, but Kira was a benevolent god, occasionally deigning to impart his genius for the betterment of humanity (but only for the good people who deserved it). Additionally, when Kira officially became god of the new world it would be nice to have scientists on his side. Maybe after he had weeded out all the criminals and bad people he could start improving science by cleaning out all the incompetent scientists…
Light sipped his tea and smiled politely at the grad student across from him. Ketsu Mori, currently majoring in biochemistry. She was working on a research project studying the effects of catalytic enzymes on metabolism. And according to the scientific articles that she had given him, she was also studying artificial sweeteners. Interesting.
He frowned slightly at the thought. All this talk of metabolism reminded him of a certain sugar-addicted-detective. The amount of sugar that L consumed was positively revolting. He spent most of the day dangling one sweet or another in front of his mouth, only to slurp it up with a disgusting noise. The taskforce members sometimes took bets as to how many sugar cubes L could fit into one cup of coffee. It was amazing that the detective hadn't gotten diabetes, or had every single tooth rot and fall out of his mouth. Even worse, he never seemed to gain a single pound no matter how much he ate. Light had to exercise and eat healthy to maintain his weight. Life just wasn't fair.
Light finished reading a paper detailing the various catabolic pathways, and started on another that detailed energy use and storage. He took notes at all the relevant points, mostly for Ketsu, since he would be able to easily remember everything he read, but she might want notes later.
If most people burn energy, he imagined that L's metabolism must be a frickin inferno. Like one of those trains from an old movie. No matter how much coal was shoveled on the fire, it just kept going faster, burning. Most people's bodies would store fat when excess energy was generated, but not L.
Light finished reading the last of the papers and started going over Ketsu's research proposal. It was an intriguing project: she wanted to synthesize a compound that would eventually help people with metabolic problems lose weight. She had started with an artificial sweetener, then added a catalytic enzyme. The idea was that someone could sweeten their food without calories, and even burn more calories by speeding up the break-down of the rest of the food they ate. There had been encouraging results in the in vitro test run, and then she had moved on to rats.
"So I tried adding the catabolic enzyme enhanced sucralose as a dietary supplement, hoping that it would stimulate the metabolism of the rats," Ketsu explained. "But it seems to have had the opposite effect."
"Really?" Light leaned forward. His interest was no longer politely feigned.
"Yeah. All the rats that received the extra compound gained twice as much weight as the control group."
"Wow that's amazing." Light's mind raced at the possibilities. If this substance had caused such a dramatic weight gain in rats, maybe it would have a similar effect on humans. Maybe… maybe it would even slow down L's monster metabolism. He wondered what the detective would do if he mysteriously started gaining weight. Perhaps if he felt he wasn't in control of his own body, his confidence would decrease. It might distract him from the case and give Light the edge he needed to outmaneuver him.
"Yeah, I guess it is kind of interesting," Ketsu continued. "It must make the body go into starvation mode and start storing as much energy as possible as fat. Which is kind of interesting since some studies on artificial sweeteners and cutting calories have hinted that might happen." She sighed. "I know my findings are probably good enough to publish, but I'm still kind of bummed that the compound didn't work like I wanted it to."
"I wonder what would happen if you tried making a molecule that temporarily bound up some of the catalytic enzymes. Maybe the body would overcompensate and use up more energy."
Ketsu brightened at the suggestion. "Hey, that's a great idea. I'll have to try that next."
"Hmm, do you think I could visit your lab sometime?"
"What? Oh sure, that'd be great!" Ketsu exclaimed. "Let me know if you need anything to pay for your time. You've been very helpful."
"I'm just glad I could be of assistance." Light bowed and smiled politely. "But if I think of anything, I'll let you know."
Three days later, Light had a 2 kilo supply of beta-sucralose. It was finely ground, and looked identical to regular table sugar, but was about ten times sweeter. Even better, it was an undocumented substance, and if any lab tested it, they'd probably think it was just regular sucralose. It was also a substance that had never been used on humans, but it was about time that L played test subject for once.
"L, the rules of the game are about to change again," Light said with a malicious smile.
~o~
Ironically, the hard part would getting L to eat the sweet stuff. Light knew that as a suspect, L would be suspicious if he suddenly brought in a batch of sweets, and would probably make the other task force members eat it as well. He might even turn it into a game of "If you don't eat this, your Kira percentage will rise," for his prime suspect. Light shuddered at the thought.
No, the best way to get the sweet compound to L was to utilize another task force member. But how? Then Light had an idea. It was such a brilliant idea, that he might have been surprised, if his own brilliance was ever capable of surprising him. He would use L's disgusting habits against him.
Light could practically visualize L plinking one sugar cube after another into his coffee cup, thoughtlessly sloshing the liquid around and making stains that Matsuda or Watari would have to clean up later. Light chuckled quietly. "L, do you know, being such a slob is going to be your downfall?" he whispered to himself.
~o~
Light arrived earlier than usual at the hotel in order to put his plan into motion. As planned, Matsuda was the only other task force member in the kitchen area, cleaning up and preparing the food. Apparently, Watari, L, and the others were off watching surveillance videos in another room.
"Hey, Matsuda, do you want help making coffee?" Light offered.
Matsuda looked up, surprised, then smiled happily. "Sure, Light." Then he looked down. "But, ah, don't you have something more important to be doing?"
Light decided a little flattery might go a long way. "Matsuda, I know the others don't always appreciate everything you do, but I just wanted to say that I do. Every job, no matter how insignificant it might seem is essential and important in its own way." Light paused in his flattery to give Matsuda a brilliant smile. "I think it admirable that you are always willing to do the less glamorous work."
Matsuda blushed. "Thanks, Light, that's very kind of you."
"If L worked all by himself, imagine what a pigsty this place would be by now."
Matsuda laughed and brightened up. "You know, you're right, Light. If no-one else wanted to get the food or clean up it'd never get done."
He arranged the cups and serving plates, then picked up the jar of coffee grounds at the most opportune moment. "Hey, Matsuda, I have an idea, why don't we just mix sugar into L's coffee grounds? Then his coffee will be sweet enough to start with, and he won't have to waste so much time mixing sugar cubes into his cup."
Matsuda thought about that for a moment. "That's great idea, Light!"
Yes, Matsuda would definitely be in favor of such an idea, especially since the detective was often stuck cleaning up the numerous coffee stains that L made throughout the day.
Then he paused in thought for another moment. "But the rest of us can't drink coffee as sweet as L likes his."
"That's okay, we can just keep his coffee separate," Light said smoothly.
Light labeled a container "pre-sweetened coffee" and started mixing the beta-sucralose into the grounds.
Matsuda stuck a finger in the sugar and tried a few grains. "Wow, that's really sweet," he exclaimed.
Light's eye twitched as he carefully suppressed his annoyance. Fortunately Matsuda hadn't ingested enough to notice a difference in weight gain - he hoped. It took about five seconds to come up with a convincing lie. "It's finely ground sugar - it tastes so sweet since it has increased surface area."
Matsuda looked impressed. "Wow, you're so smart Light! You'll probably be the smartest detective in the whole world after you graduate from college." Matsuda scratched his head. "Well maybe the second smartest after L."
Light glared at Matsuda briefly before he could stop himself.
Matsuda laughed nervously. "Or maybe you'll be smarter than L, I don't know, I have trouble telling which genius is smarter."
Light forced himself to give Matsuda a pleasant smile. "Thanks, Matsuda."
~o~
L poured himself a cup of coffee, then grabbed a sugar cube to plop into the liquid.
"You don't have to add any sugar, Ryuuzaki," Matsuda happily informed him. "The coffee has already been sweetened."
"Indeed," L said blandly.
"Yeah, Light helped me come up with the idea. We mixed sugar in with your coffee grounds so now you won't have to spend so much time mixing in sugar cubes."
Light mentally face palmed. He had hoped Matsuda would forget to mention him. Maybe manipulating Matsuda hadn't been that great of an idea. But there was nothing inherently suspicious about adding sugar to coffee, was there? "I thought it would be a more efficient use of your time," Light said innocently. "And now Matsuda won't have to clean up so many coffee stains."
L gave Light a suspicious stare, but carefully sipped his coffee. From the look on his face he didn't taste anything out of the ordinary. Then he gave Light a defiant glare and deliberately added one sugar cube. "It's not quite as sweet as I like it," he informed them. He sloshed the coffee around on purpose as he stirred in the sugar. L was such a brat sometimes.
~o~
Light carefully closed and locked his bedroom door behind him before allowing himself a victorious smirk. It had only been two weeks since he supplemented L's coffee, and already he was beginning to see results. They weren't very obvious results, and no-one else had probably noticed, but Light's trained eyes had picked up on the fact that L's baggy jeans didn't sag as much as they used to, and the detective's cheeks were starting to fill in and puff out.
He was still having a hard time keeping ahead of L with the second Kira/Misa fiasco, but he'd eventually win that one as well.
Light smirked again and imagined L gaining more and more weight. Would he wonder what was happening? Would he figure it out?
Light had outsmarted him, and without even using the death note. L was in his power and he didn't even realize it yet. He considered using the death note to send another message: "L you seem to be gaining weight," or "L, do you know, sugar is bad for your health," or perhaps he could have Hideki Ryuga make 23 days of pop songs about overweight detectives. It was almost worth the risk of getting caught.
Yes, the death note was merely a tool, Light was the smarter genius here.
Light glanced up at the Shinigami who was staring at him, being entertained. "Ryuk, you're really lucky I'm the one who picked up your death note."
Ryuk laughed. "Yeah, I'm sure no-one else would be as modest as you are."
Light gave Ryuk a quick glare, then went back to plotting world domination.
He should probably be using this time to judge criminals, but gloating was just so much fun. Light flopped onto his bed and laughed. He imagined a chubby L ineffectively chasing after Kira. "L, how fast will you be able to run after you gain 30 kilograms?" He rolled and laughed some more. It was too perfect, he controlled L's body, he could do whatever he wanted and get away with it, he was smart enough to pull it off.
Light rolled around on the bed some more. He imagined L's wrists filling out, his cheeks getting chubbier, and his ass sticking out. "L," he gasped. He felt pleasure building, like when he used the death note, but more intense. Gathering and growing. "L, ah, L." He thought of L, powerless, staring up at him and realizing that Light had done this to him, Light had absolute control over him, and then he would submit to Light and Light would win and he could do whatever he wanted and L might try to fight back at first but he would be powerless and then he would– "Ah!"
Light looked up and was mortified to see Ryuk hovering over him. Not that the Shinigami hadn't seen something like this before, but this was the first time Light had gotten off while thinking of L. ! Light blushed slightly at the implication.
"Light, did you just-"
Light threw a pillow at Ryuk.
"Hyuk, hyuk. You humans really are entertaining."
Light gave the Shinigami a murderous glare. "Shut up, Ryuk."
Then the god of the new world went off to change into a pair of clean underwear.