All right, here's a fun story:
I've written lots of fan fiction before. Mostly because I wanted to, recently because I was paid to, sometimes as a favour. This is the first time I'm writing one because I am trying to impress a girl. This is officially me launching a new project- a Death Note/Doctor Who crossover. For the very few people out there who have seen both those shows, I hope you enjoy. For those of you who read it anyway... thanks, and I hope you're not too confused. :D

Without further ado:
*Doctor Who theme intro*

Through the time vortex, a space outside the normal space-time continuum yet simultaneously part of it- it's complicated, just roll with it- the TARDIS flew. A Time Lord would have marked it as a type 40, basically a museum piece- but of course, there were no Time Lords left to make that observation, save for the one piloting this particular TARDIS.

Said Time Lord being well in his nine hundreds, appearing quite youthful and vigorous for his age- and at the same time wearing the most dreadful, out-of-date fashion imaginable, at least as far as Amy Pond was concerned. Time was, of course, completely relative in the TARDIS, so it was possible it was at once quite fashionable to wear suspenders and tweed- and completely out of style. Amy knew which side she was on. And still, that dorky, youthful face with the ridiculous clothes held an intellect unlike any she had ever seen, the kind of mind that would save worlds and be back for tea time.

At this exact moment, though, they were crashing. Not for the first time- they seemed to do this a lot.

"Hang on!" The Doctor cried, feverishly tinkering with wheels, panels and buttons on the hexagonal control panel of his TARDIS, barely staying on his feet as the machine cringed and spun. Amy, for her part, only barely remained upright. Her husband Rory was less lucky, having been flung to the floor by an especially vicious twist.

"Doctor, what's happening?" Amy cried, feeling angry- that special kind of angry when things were just never going according to plan because the damn TARDIS would never work right, but it was all part of the charm, somehow.

"Do you even need to ask?" Rory groaned. "We're crashing- probably into a fleet of mutant vampire aliens. Again."

"Now, Rory, there's no call for that kind of attitude. I got you out perfectly safe and almost completely sound." The Doctor protested absentmindedly, as he spun a wheel rapidly. "Hang on- we're materializing!"

And suddenly the rumbling and shaking stopped, and the brilliant time machine let out that characteristic, wheezing groan. They had landed.

"Well, thank god for that." Amy said. "Where are we, anyway?"

"I have no idea!" The Doctor said cheerfully. "Let's find out."

"Do we at least know what planet it is?" Rory mumbled, getting to his feet. "We don't want to barge into some kind of gassy acid planet populated by cyborg slugs."

"Don't be absurd, Rory. That never happened." He looked a bit thoughtful, and straightened his bow tie. "Well, maybe there was this one time…" He shook his head. "No, anyway, we're on earth. In your time, even, give or take a few years." Seeing Rory's face, he added, "And by "a few years", I don't mean "a few decades".

"Well, good then."

"And where are we?" Amy asked.

"Now that we still have to find out." The Doctor said cheerfully, and he had that glimmer in his eye, almost like a child on Christmas- that love for finding new places, new things, always in constant amazement of the universe's things great and small.

Deciding not to be outdone, Amy marched out first. It was a bit shocking, almost- after having seen all the wonders and most strange alien sights, a modern human city seemed kind of boring. Cars in the streets, people positively everywhere, giant skyscrapers… this was definitely home. Ish.

"Well, we're definitely not in England." Rory remarked. The TARDIS would translate any language for them, but there was a lot about this place to suggest this wasn't any place she was familiar with. Like how everyone in these very busy streets looked Asian.

"Tokyo, Japan!" The Doctor exclaimed. "The year twenty-o-seven. Good year. Only had to save the planet once last time I went."

"But… why are we here?" Rory wondered. "Usually there's some alien invasion of some kind."

"Oh Rory, don't be so pessimistic!" The Doctor said, leisurely walking down the street, against the stream of people. "Sometimes a crash landing is just a crash landing, you know."

"We should be so lucky."

Ignoring him, the Doctor kept walking, his two companions following close by. For once, the Doctor didn't look too out of place- most men wore suits, although none seemed to wear bow ties. Which the Doctor would insist, till he regenerated, were cool.

After a little while, the Doctor stopped in front of a TV store. He gave a screen a funny look, and walked into the store. Amy and Rory quickly followed him in.

"What is it, Doctor?" She asked.

"Thought I saw something off." He mumbled, walking up to one screen. "Here, listen."

The TV presenter, a stern-looking man with glasses, was reading the news.

"…it is reported that yesterday, one Manzo Kusoku died from a heart attack. Kusoku was under suspicion of criminal activity and ties to the yakuza, and was recently charged with three cases of murder, but was acquitted due to a lack of evidence. This is the fourth suspected yakuza to die from a heart attack this week, and the public continues to speculate that these seemingly random cases of fatal heart attacks afflicting only criminals are orchestrated by some kind of mastermind."

"…oh dear." The Doctor said.

"I'm going to guess he's a cyborg alien from Saturn." Rory mumbled.

"Doctor, what is this? Do you know what's going on?" Amy asked.

"No- well, I do. A little. Last time I went to this particular year, I do remember a big hullabaloo- people upset, word about some "Kira" character. I sort of forgot about it, since I was busy fighting off a zygon invasion."

"Zygons?"

"Starfish-looking humanoids. Shapeshifters. They were trying to mount a telekinetic submission ray on the moon to force all of earth's population into slavery. Took some fidgeting, but I managed to destroy it."

"Is it bad that that sounds completely normal and believable to me?" Rory asked.

"It's not just you, honey." Amy reassured him. "Still, are you going to do something about this?"

"Well, it's worth looking into. I mean, criminals dying at random? Sounds like we've got a mystery on our hands. And I intend to try and solve it."

Said solving of mysteries was, of course, easier said than done. After half an hour or so of walking around, seemingly at random, with the Doctor every now and then flicking out his sonic screwdriver, they finally came upon what looked like an internet café. They walked in, the Doctor waved his psychic paper at one of the employees, and the three of them got seated.

"Would you mind telling us what we're doing here?" Amy asked.

"I," the Doctor said, pacing back and forth, "need to think a little. Maybe make a couple of calls- I think I'll call U.N.I.T, see what they know. Maybe Torchwood. Meanwhile, I want you two to do some research!"

"…how?" Amy frowned.

"Amy, you've got the internet at your fingertips. There's a whole host of information just a mouse click away."

"We're travelling in a multidimensional time machine surpassing all of modern science, and he tells us to use Google…" Rory muttered.

"Well, for something like this, there could actually be a lot of gossip- we might not find out who this killer is, but we can definitely get a good idea of what's going on." Amy said, all chipper.

"Right." Rory said, sounding skeptical. "Well, let's get to it. I know how to surf the internet, at least."

"Good on you both." The Doctor said happily. "Now, if you'll excuse me…"

One phone call later, and he wasn't very pleased. U.N.I.T didn't know much more than he already had seen here- string of deaths, all targeted at criminals, almost all of them heart attacks, almost all of them in Japan. Granted, Japan specifically wasn't exactly their area- he kept forgetting how primitive and divisive humans could be. Still, they had promised him to let him know if they'd find something new out. Torchwood didn't know much either, although they did have an investigation ongoing- so much for that. This was a bit irritating- why couldn't it be Daleks, or weeping angels? Daleks wanted to kill you, and the angels wanted to feed on your potential lifespan. They were direct. Still, he had cracked tougher nuts. He turned his attention back to Amy and Rory, who were diligently checking the web.

"Find anything useful?" He asked, leaning in over Amy.

"Lots, actually." Amy said, leaning back. "Some of this is seriously creepy. There's this whole online cult following of 'Kira'- that's Engrish for 'Killer', if anyone missed that. Some people think he's like a superhero who punishes evil, some think he's punishing the people the law can't, and some kind of talk about him like he's a god."

The Doctor's eyes narrowed, as he took a closer look. It was some sort of internet forum, filled with comments- people getting lyrical about this 'Kira', about this… murderer. It was a bit distressing to watch.

"What do you think, Doctor?"

"Well," he mumbled, "I've never seen any gods. But I do know a pattern when I see one- someone or something must be doing this intentionally. Rory, did you find anything?"

"Um, yeah." Rory said, pulling up a tab. "Aside from the creepy fan club, there's this whole archive of people who got killed, what they did and when they died… Doctor, that's a lot of people. Dozens, easily."

The Doctor nodded. "I see. Well, it's about time we took the bull by the horns. Rory, could you check if there's a police station nearby?"

"Sure."

A quick search later, followed by the Doctor assuring the two of them that he'd memorized the map- he probably had- the three of them were off. After an all too long walk of trying to avoid shoving people- difficult, with the streets jam-packed with people on their daily business- they finally arrived at the police station. Confidently, the Doctor strode up, into the station, and walked up to an officer sitting behind a desk, reading a paper.

"Hello!" He exclaimed spiritedly. "I need to find whoever is in charge of you. And then his boss, if possible. Actually, if you could take me to the national chief of police that would be fantastic. But I don't suppose you could, no?"

The officer gave them a look like he was some insane tourist- which, to be fair, wasn't that inaccurate of a description- and decided to ignore him, going back to his paper.

"Oh, don't be like that." The Doctor continued. "I need to speak to your boss. And did I forge to mention…" he dug up the psychic paper from his pocket, dramatically flinging it in the officer's face. "…that I am in fact with Interpol! Ha, bet you didn't see that coming!"

The officer's eyes widened, and he got to his feet. "I'll take you to see the chief at once, sir. Right this way."

"Splendid!" The Doctor said cheerfully. "And don't mind these two- they're my subordinates. In civilian dress, of course."

The officer nodded, and they were soon led to the chief of police. Said chief, not unexpectedly, didn't know much of anything about Kira- but he did send them on their way towards somebody who did, hopefully, and before long they were travelling in a police car towards whatever special unit was investigating this Kira case.

"You don't think they'll double check if there really is an Interpol agent called the Doctor?" Rory wondered.

"That's a problem for later." The Doctor said casually. "Right now, we're making progress. Isn't this exciting?"

"Well, we're not in immediate danger of being killed, so I guess it qualifies." Amy remarked.

"Yet." Rory said dryly.

A little while later, they stood before a skyscraper, presumably an especially fancy police building. They were escorted in by an officer, and Amy did her best to take it in. Police buildings weren't the most exciting sights she had seen, but then again, it was a nice change of pace compared to dirty dungeons, sterile alien environments or mutant alien cyborgs. Soon, they were all in an elevator, headed up towards whatever stop was next.

Police Chief Yagami Soichiro had been under quite a bit of stress recently. Handling the Kira investigation was a hefty responsibility, and for the longest time he'd been fumbling in the dark with no clue what to do or where to go- was Kira even human?

And then the mysterious L had come into the picture, first as an anonymous computer screen with a voice, and more recently as a somewhat autistic young man with a penchant for walking barefoot and eating cake. And because of him, they had a shot, a chance to investigate with success. It had been… strange to be outdone by somebody that much younger and smarter, but if it meant Kira, he'd gladly take the lead of that great, big… weirdo.

Still, his stress levels stayed consistently high- he worried he might develop an ulcer. Which was why, walking into his office, seeing a young man sitting in his chair, feet splayed up on his desk, he wasn't feeling particularly tolerant.

The young man certainly wasn't Japanese- probably American. He looked like a dumb tourist of some kind, and behind him were two other Americans, equally as tourist-looking.

"Who the hell are you?" He began. "And what the hell are you doing in my office?!"

Quickly standing from the chair, the young man flashed an ID card. "I'm with Interpol. Look closely, see?"

Soichiro looked close, adjusting his glasses. The badge looked legitimate- it named one inspector John Smith, an alias no doubt. But Interpol had mentioned nothing about sending an agent, let alone three, to aid him.

"John Smith." Soichiro grumbled.

"That's me!" The young man said cheerfully. "But you can call me The Doctor. Or just Doctor, if you prefer it." He smiled. "Now! I heard you were having trouble with some suspicious, supernaturally skilled killer, and that's just the kind of thing I'm good at."

"…yes." Soichiro said, making a note to double check with Interpol as soon as possible.

"Now!" The young man continued, "What exactly do we know? I did hear bits and pieces, but it's really not much more than 'criminals die mysteriously in heart attacks'."

"Doctor." Soichiro said, frowning a very serious kind of frown; the kind that took years of practice and could intimidate interns and reduce criminals to a quivering, nervous mess. In theory, at least. "I really have to wonder why Interpol has to send aid. This is a closed investigation- we don't need outside help."

They did, in the form of L, but there was no need to mention that.

"Oh, I think you do." The Doctor said dismissively. "Because if I'm right, you're mainly just fumbling about in the dark. Just like me- so why don't we fumble together? Two heads are always better than one, they say. Or was it two hearts?"

"Doctor-" Soichiro began, but the obnoxious young man cut him off.

"Soo, what could cause this, eh? Maybe some sort of theta-Thaegan telekinetic wave activity- although the Thaegans are all extinct. No, wait- in this time they're not, but they're at least two galaxies away. Why would a Thaegan be here, anyway? That's just silly. But something is causing this. What could possibly manipulate a human body from afar? I mean, I could think of at least seven things off the top of my head that could, but nothing that fits this timeline. This is mysterious. I like mysterious." He grinned.

"Don't worry, you get used to it." Said one of his companions, a tired-looking man. "If you feel like strangling him, that's a perfectly normal sign of him being himself."

Soichiro was reaching that point, but he was a man of restraint. "Doctor," he began, keeping his temper even, "I don't know what US state you're from, or how they do things there-"

"Gallifrey, actually." He interjected.

Soichiro frowned. He had never heard of a state called Gallifrey- but then again, he didn't know western geography all that well. "I don't know how things are done where you are, but over here, we do not just march in on delicate, top secret investigations."

The Doctor sighed. "Oh, you humans can be so stiff sometimes." For a moment Soichiro thought he had said 'you Japanese', but he'd said 'you humans'. What was he on about?

"At the very least, I demand you tell me your qualifications. Where did you graduate? What experience do you have with high level criminal investigation?"

"Oh, I am plenty experienced." The Doctor said cheerfully. "It's not always criminal investigation, mind you, but that does happen often enough. There was this one time I tracked down Jack the Ripper- although he turned out to be a man-eating lizard from outer space."

Soichiro looked at him with eyes slightly widened. This man was either eccentric- very eccentric- or quite mad. And yet, there was something fascinating about him- he was surprised he was even humoring him this much. "Doctor-"

"So, I repeat- what do we know?" The Doctor said, beginning to look around the office, checking through files.

"Not a whole lot, Doctor." Soichiro grumbled. "And stop doing that!"

Ignoring him, the Doctor rummaged through Soichiro's desk, until he found a file about Kira- it hadn't exactly been hidden, and it was the most recent one. It didn't really contain all that much data- they really didn't know all that much yet. Still, this breach of privacy was a bit much.

"Give me that!" He snapped, reaching for the file.

The Doctor held it out of his reach, and flickered through it quickly. "What do you know- you really don't know a whole lot about this Kira character." The Doctor said, sounding almost smug. "You managed to figure out where he'd live in Japan, very roughly- that's better deduction than I would have expected."

Soichiro quickly grabbed the file, tearing it from the Doctor's hands. He had only eyed through it- had he just happened upon the right place? No matter what the case, this was a bit much.

"Out." He said coldly. "Get out, now."

The Doctor looked at him, puzzled. "No, you don't understand- there's a killer out there, and I have to stop him. It's what I do." He sounded serious- so very serious, and there was something in his eyes, like he was older than his years by far. But no matter how convincing he was, enough was enough.

"Get out, or I will call security to escort you out." Soichiro said coldly.

The Doctor sighed, and shrugged. "All right, all right, we'll leave." He gave Soichiro a look, and sounding quite serious, he said,

"Good luck, Soichiro."

Five minutes later, the three of them were in the lobby of the building, the Doctor moping. He wasn't admitting to it, but it was definitely a mopey kind of gait on him as he walked toward the building's exit.

"Well, that was rude." He grumbled. "Silly humans- so stingy, aren't they?"

"You were rude, Doctor." Amy remarked. "Just walking in there and acting like you know what you're doing isn't going to work a hundred percent of the time."

"It usually does." He said grumpily. "And… I had a look at that file. They're working with very little- they're grasping at straws, and still they somehow managed to narrow the criminal down to one specific area. Either that policeman is cleverer than he lets on- or somebody clever is helping them."

Then, his face lit up in a grin. "But if talking fast doesn't work…"

"What, Doctor?" Rory asked. "You're going to do something, aren't you? Well, at least this time we're not running away from something trying to kill us.

"I have a plan." The Doctor said mischievously. "Just follow me."

Soichiro sat at his desk, drinking a simple mug of coffee. It would probably not be good for possible ulcers, but it kept the stress quite manageable. That Interpol agent… he had ordered Ukita to give Interpol a call, and though there had been no reply yet, he was doubting that this "Doctor" was what he said he was. Unless, of course, he was some kind of eccentric genius, like L- that was a man he'd never have thought was a genius detective, had he not known it from evidence. He sighed. This case would be the death of him…

Then suddenly, his contemplations on weak evidence and straw-grasping was interrupted. It began like just a small oddity- a gust of wind, which was strange for a room with no windows open. But before Soichiro had even had the time to get properly surprised, a wheezing, hissing groan filled the room, a hideous noise that seemed to come from everywhere and nowhere. The wind increased, and the papers on his desk fluttered around, spreading all over the room. And before his eyes, the shape of a blue box began to form, fading into reality from nothing. Soichiro gasped; he was not easily surprised- but this was like nothing he'd seen before. Quickly, he checked his memory. Was there any possibility he was drunk? No, he hadn't had a drink in ages now. Was he on drugs? If so, he had no memory of using any. Was he dreaming? That was possible, but no dream had ever felt quite so real.

Then, his moment of shock was interrupted, as a door opened from the blue box- and from out of it, the young man from before stepped, with a swagger in his gait. Following close behind him were his two companions from before.

"I know I wished you good luck," The Doctor said with a grin, "but I decided I couldn't just leave you all on your own. I mean, mysterious, supernatural killers, really? That's a bit much for normal detectives, don't you think?"

Soichiro breathed heavily. "You- what- you!" He managed, standing himself up.

"I know." The Doctor said smugly.

Soichiro took a deep breath. "Blue boxes don't just… appear out of nowhere." He said, forcing himself to be calm. "That isn't possible."

"Oh, you've seen nothing yet." The Doctor said excitedly. He turned, and walked back into his box. "Come see here for yourself."

Not sure what to expect, Soichiro walked toward the box. What could there be? A box that size couldn't fit many people- but boxes usually didn't appear out of thin air.

"Well, come on!" The Doctor said impatiently. Hesitantly, Soichiro poked his head inside the door-

And what he saw was, by every standard he'd been taught, impossible. It led into a huge room, much bigger than his office, and at its center were a hexagonal console of some kind. Quickly, Soichiro poked his head back out, looking out and around the box. It still appeared to be- just a box. No wider than a meter or so. He poked his head back in, and dared to step inside.

"This… is impossible." He mumbled.

"I'm tempted to ask if you have any passing remarks- but we'll let that be for now." The Doctor said happily. "And I think by now, you may begin to suspect that I am not actually with Interpol."

"Hadn't crossed my mind." Soichiro said honestly.

"Well, I'm not- but I'm sure UNIT would give me a good reference." Snappily, he walked around the console, and back towards the exit. "This is the TARDIS. This is my ship, and it goes wherever- and whenever- I need to be. For now, it took me here. That means I'm needed here and now- now I have to ask you, will you let me help you?"

There were those eyes again- so strangely old, and so strangely compelling.

"…what can you do?" Soichiro asked, determined not to let himself be run over.

"Good question!" The Doctor asked. "I'll tell you on the way to the investigation room. You have an investigation room, right?"

Before Soichiro had a chance to reply, The Doctor had marched out of the box- the TARDIS, apparently- and Soichiro, after looking around for a moment, taking in all of this physically impossible ship, followed him.

"There is- but I didn't say I'd take you there." Soichiro grumbled, walking out of the office with the Doctor at his side.

"Oh, but we're headed that way, aren't we?" The madman with a box said confidently. "Come along, Ponds."

And somehow, Soichiro found himself leading this strange 'Doctor' to the room where the investigation was centered. Most of his men were there; Matsuda, Mogi and Ukita. And, sitting on a couch, enjoying a piece of strawberry cake, L.

The Doctor strode in confidently, having a look at the people there. "So these are your detectives? Well, I've seen worse- we'll make this work somehow."

Then, he shot L a look, and there was a strange look on his face, one of recognition. L himself stood up.

"Professor Smith?" He said. "What are you doing here?"