Okay, story time! One day, I was sitting around, reading Shizaya fanfiction when I realized that there were no fics that had Izaya or Shizuo switch bodies. I've always loved fics like that and I thought that it would be quite amusing if something like that happened to the two men in Ikebukuro that hate each other with a passion. The title is inspired by the song "Running Up That Hill" which has been performed by Kate Bush, Placebo, and Within Temptation. In the song, it says "And if I could make a deal with God and get him to swap our places..." and for that reason, I thought it would make a reasonable title for a fic like this.

This is the second fic I've written for Durarara and I hope I've gotten everyone in character. Later on, there might be some situations were some people get out of character and this will develop into Shizaya just to warn you. Hope you enjoy!

Chapter 1

It was an average day in Ikebukuro. People were crowded on the streets, walking to work, school, or just for an outing. A few teenagers hung out on the street corners, talking about crushes or last night's homework. Simon Brezhnev stood outside of the Russian sushi restaurant, trying to hand out flyers to whoever passed by but this usually ended in many potential customers fleeing out of fear.

Across the street from the restaurant, Mikado Ryuugamine and his friend Masaomi Kida were walking to school peacefully. Masaomi glanced at his cell phone and frowned.

"They're late," he sighed, staring at a nearby street corner in disappointment.

"It doesn't matter," Mikado said to his friend. "We'll be late to school if we wait for them…"

"But Mikado!" Masaomi protested. "What about our morning entertainment? We need something to laugh at before we resign ourselves to the dreary halls of school! Don't you agree?"

"Masaomi-kun, they're not coming today," Mikado said, shaking his head and beginning to walk forward. "Maybe Izaya-san finally took into consideration how much fun a broken neck would be. Besides, I'm sure that there are more important things to do than sit around and wait for him to…"

Mikado was cut off by a park bench flying through the air and landing inches from where the teenage boy was standing. The dark-haired boy made a small squeak and stumbled back, landing clumsily on his ass. Masaomi ran up to him, a bright smile on his face.

"This is it!" he said excitedly. "Here's our entertainment for the morning!"

A yell broke out through the morning air, causing everyone on the streets to scatter in fear.

"I-ZA-YAAAAAAAAAA!"

Following the yell came a man, laughing maniacally as he bounded away from the bench and into the street. Cars screeched to a halt to avoid hitting him and drivers poked their heads out to yell at the man but stopped upon seeing who it was.

The laughing man twirled around as a traffic sign was thrown at him, his furry coat twisting with his thin body. His red eyes gleamed with excitement as his rival stepped out from behind the bench. He was ready to play his favorite game, one that he could only play in the streets of Ikebukuro.

"Oopsies~!" he giggled. "Looks like you missed me, Shizu-chan! You need to work on your aim."

"Shut up, flea!" the blonde man clothed in a bartender uniform roared, clutching a stop sign in his hand. The metal bent like flimsy aluminum under his strong fingers and his eyes burned with absolute hatred. "I thought I told you to never come here ever again!"

"Hmmm… Oh dear, my hearing must be getting worse with age…" the dark-haired man sighed dramatically. "Listen, Shizu-chan, I only came here to visit with Shinra and get something to eat at my favorite sushi restaurant so I don't have time for you. Sorry~"

"Spare me the lies, Izaya," Shizuo Heiwajima, the strongest man in Ikebukuro, snorted. "I know why you're really here."

"Oh~?" Izaya Orihara, the most dangerous man you could ever meet, replied and raised a thin eyebrow. "Really? Then why am I here, Shizu-chan?"

"You're only here to cause trouble," Shizuo snarled, taking his cigarette from his mouth and throwing it on the ground. The cancer stick soon met its end underneath his shoe as he ground it into the pavement. "And I told you not to call me that! My name is SHIZUO HEIWAJIMA!"

He flung the sign at Izaya, who simply dodged it at the last second. The dark haired man flashed another smart-ass grin at the blonde and ran off, making his way towards a secluded alley way. With an angered roar, Shizuo ran after him at top speed, his mind set only on killing that damned flea for once and all!

Back on the street, a terrified Mikado was still trying to process what had just happened while Masaomi jumped up and down in delight.

"I knew they would make it!" the blonde cheered. "It wasn't too impressive this time but those two never fail at making an exciting entrance! Right, Mikado?" He looked over to his friend, who was still sitting on the ground and shaking violently. "Mikado?"

"L-let's just get to school…" the dark haired boy sighed, getting up shakily. He reminded himself that he should probably find another route to school that didn't involve almost getting killed every morning.

…

"I-ZA-YA-KUUUUUUN!"

Izaya laughed to himself as he ran through the streets of Ikebukuro, the blonde brute following closely behind. He never could tire of their little game. Shizuo was just too easy to get fired up. It was like throwing a match into a tank of gas; Izaya would push and push until the other man exploded and threw something dangerously heavy at him. That was what made their game so fun.

He leapt into the air, anticipating the sign being thrown at him from behind. Gathering his legs beneath him, he chuckled as he watched the sign soar underneath his feet and bury itself into a nearby wall. He landed on the ground gracefully, like a cat, and prepared to take off again…

What the informant hadn't anticipated was that Shizuo was suspecting that he would miss Izaya the first time so he had decided to throw a large vending machine at the distracted informant.

The vending machine smacked into Izaya, forcing a pained cry from the informant's lips. Shizuo's face broke out into a malicious grin. He had him; he finally had that damned flea! He approached the vending machine, watching as Izaya struggled helplessly underneath it. The dark haired man's eyes widened in alarm as Shizuo approached and he whipped out his knife, hoping that it would give him somewhat of a way to defend himself.

"Well, well, well…" Shizuo smirked, squatting down so that he was eye-level with the louse. "Looks like I got you this time, Izaya-kun."

"Lucky shot," Izaya spat, trying to wriggle his way out from under the machine. He was having no luck so far due to most of his lower body being caught under the offending piece of metal. "So, Shizu-chan, are you going to try and kill me now?"

"Doesn't sound like a bad idea," Shizuo smirked and took his sunglasses from his breast pocket, pushing them onto his face. "But for now, I'm satisfied with watching you squirm."

Izaya glared at him, the expression making Shizuo snicker. The informant pushed as hard as he could against the vending machine, trying to free his legs. He cursed his lack of muscular strength as he pushed and pushed, only managing to move an inch from under the machine.

"Shit…" he cursed as a sharp pain shot through his leg. Damn that protozoan! He had probably broken his ankle.

"Having fun?" Shizuo asked, lighting a cigarette.

"Fuck you."

The blonde chuckled and took a drag from the cigarette, making sure to exhale in Izaya's face.

"Don't do that!" the informant coughed, gagging on the smoke. "How can you stand those things? They're disgusting!"

"They help me relax," Shizuo shrugged. "I'll make sure to blame you for causing my stress when I get lung cancer."

"Ha, ha," Izaya snorted as he managed to move at least a couple more inches out from under the machine. Just a few more… "You're a horrible person, Shizu-chan."

"And you're any different?"

Izaya glared at the floor. "Touché." He paused as he managed to free his left thigh. "I'm going to kill you when I get out of here."

"I'd like to see you try."

"You know, Shizu-chan…" Izaya sighed as he freed his right thigh and knee. "You really are a monster." Shizuo paused, the cigarette almost to his lips. "I mean, really. You do things without thinking and you hurt people without meaning to. And it's all because you have a short fuse. Interesting, isn't it? Maybe you should get some anger management classes." He could see that his words were angering the blonde man, due to Shizuo's shaking frame. "Ne, Shizu-chan…" Izaya smirked, deciding to drive in the final nail. "How's your brother, Kasuka? He hasn't gotten into any trouble, has he? You know, the other day, there was a man asking me about Hanejima Yuuhei… I may have let a few things slip…"

Shizuo's reaction was faster than he expected. Before he knew it, Izaya was lifted out from under the vending machine and was held close to Shizuo's face, the blonde man holding him up by the collar of his shirt.

"If you do anything, anything, that would bring harm to Kasuka…" Shizuo snarled. "I'll kill you with my bare hands."

"I know this, Shizu-chan," Izaya sighed, holding his hands up in surrender. "But… you do know you just freed me from your little trap, right?"

Shizuo paused and looked at the vending machine and then back to Izaya. Izaya held in his laughter; it was just so easy to manipulate the brute! However, he was snapped out of his mental victory dance when he felt Shizuo's fist tightening around the cloth of his shirt. Maybe it would have been smarter if he had made Shizuo release him first…

With a great roar, Shizuo flung the thin informant through the air and into a wall a few feet away. Izaya grunted in pain as his back slammed against the wall with a loud CRACK! Despite the great amount of pain shooting through his body, the informant managed to pick himself up and run off.

Shizuo snarled and ran after his nemesis, determined to catch the little bastard if was the last thing he would ever do.

"I-ZA-YAAAAAA!"

…

Shinra Kishitani only wanted a normal day, just for once in his life. Sure, normal was hard to accomplish when you lived with a headless woman but hey, you could dream right? So that was why the underground doctor was relaxing on his couch, drinking a cup of tea and reading an enjoyable novel.

That was until…

"Shinra!" a voice cried and there was a great amount of banging on Shinra's apartment door. "Are you here?"

Shinra nearly choked on his tea at the sudden arrival of Izaya, taken by surprise.

"I'm in the living room!" he called out, wiping his mouth on his sleeve.

Izaya staggered in, limping on his right foot and holding right arm which was dangling limply at his side. Despite his battered appearance, he still managed to wear his trademark smirk proudly. "Ohayo," he said to Shinra, taking a seat on the couch.

"Izaya-kun!" Shinra gasped. "What happened to you?" He paused. "Wait, let me guess… Shizuo?"

"Who else would be able to do this to me?" Izaya asked rhetorically.

"Point taken," Shinra sighed. "What happened this time?"

"He caught me off-guard and hit me with a vending machine," the informant shrugged. "And then he threw me into a wall."

Shinra sighed and shook his head. Those two would probably never learn. "Come on then," he sighed. "Let me take you to my lab and get you fixed up."

"Arigatou, Shinra," Izaya sighed, letting his friend help him up.

Shinra took Izaya's left arm and placed it around his shoulders, helping the informant limp to the small lab that Shinra had in his apartment. Once there, he had Izaya sit on a gurney and examined his ankle and arm.

"Your ankle's sprained," Shinra said. "For now, you should stay off of it. And as for your arm, there's a slight fracture but nothing too serious." The doctor grabbed some bandages and took off Izaya's shoe and sock, wrapping the injured body part up. "Let me clean some of those cuts you have too."

Izaya sat there like he was being pampered as Shinra cleaned him up and applied bandages to every cut he had. As Shinra applied the last bandage, the door to the apartment slammed and a low growl came from outside of the lab.

"Izaya-kuuuuuun…"

"Oh! It looks like Shizu-chan has found me!" Izaya chirped.

Shinra sighed, putting his face in his hands. He had to admit, when they had first started fighting, it was amusing. Now, it was just tiring.

"Hello, Shizuo," Shinra greeted as the blonde ripped the door open. "I heard you and Izaya got into another fight again…"

"I'm going to kill you…" Shizuo snarled, glaring at the informant.

"Oh, Shizu-chan!" Izaya gasped in mock dismay. "You're such a brute! Trying to beat up a defenseless and injured man! How could you?"

"I could show you how…" Shizuo snarled, reaching for Shinra's desk chair.

"Whoa! Wait!" Shinra said, putting himself between the two. "Let's not start this here, okay? Let's just all relax and maybe have a cup of tea. In fact, I'll put the kettle on right now!"

The doctor quickly rushed out, leaving the two men alone. Shizuo glared at the informant, his gaze returned by Izaya's cocky gaze. The only sound in the lab was the ticking of the clock on the wall. They waited for the other to say something, something that would set off their fighting again. There was only silence…

And then Izaya opened his mouth.

"Ne, Shizu-chan," the informant groaned, stretching his arms above his head. "You really are an idiot. Not to mention a monster." Shizuo did not answer him and remained silent, staring intently on the ground. "You seem to be looking for one thing. Love maybe?" Izaya's smirk widened. "How pathetic. How could anyone ever love you?"

"Shut up…" Shizuo muttered, trying to keep the informant from seeing that he had struck an unhealed wound.

"It's because you scare everyone away," Izaya smirked and his voice dropped to a low whisper. "It's because you're a monster…"

"Shut up!" Shizuo roared and gave in to his anger, throwing a fist at Izaya.

The informant hopped aside with a smirk, landing gracefully next to the blonde. However he had forgotten about his injuries, for he lost balance on his bad ankle and fell to the ground. Cursing, Izaya scrambled to his feet only to be slammed up against a wall. Bottles clattered from the desk nearby and broke upon meeting the floor, some fumes coming from the liquids seeping into the floor.

Shizuo pinned Izaya to the wall, gripping the other's jacket tightly. His eyes burned with anger and he wanted Izaya's blood on his hands… NOW. Izaya thought fast, however, and pulled his knife out, quickly slicing the blonde across the chest.

Unlike Izaya had planned, Shizuo did not let go of him. Instead, the look on his face became more murderous and his grip on Izaya tightened rather than loosened.

"The clothes…" the blonde muttered, rage creeping into his voice. "The clothes I got from Kasuka!"

He threw Izaya onto the floor, the informant's head making a satisfying thump as it collided with the floor. This made more bottles shake and fall, splattering liquid and glass all over the two. Shizuo ignored the chemicals burning his skin and wrapped his hands around Izaya's neck, intent on squeezing every last bit of air from the man's lungs.

For the first time in a long time, Izaya actually felt scared. Maybe he had actually pushed the envelope a little too far this time. Shizuo might actually kill him this time. The hands around his throat tightened and his red eyes bugged out of his head like a squeaky toy as he gasped for air. His thin fingers pried at Shizuo's larger ones as he gagged and coughed and struggled. He kicked out his legs and hit another cabinet, knocking down some more vials and bathing him and Shizuo in whatever Shinra kept in his weird-ass lab.

The vials breaking on Shizuo's head only made him angrier and his grip tightened to the point that Izaya thought he would snap his neck. The informant saw a message in those hazel eyes…

Murder.

"Sh-Shizu-chan…" the informant rasped as he felt himself fading. "Don't… please…"

"Shizuo!"

Shizuo's hands left Izaya's throat as Shinra and Celty ran in. Izaya took this opportunity to scramble away from his assailant and leaned against the opposite wall, gasping for breath and coughing. Shizuo was taking deep breaths, his murderous look still on his face.

"What the hell were you two doing in here?" Shinra gasped as he saw the broken bottles. "Tell me in the living room. This room probably isn't safe anymore." He strapped on a gas mask and turned to Celty. "I'll clean this all up. You talk to those two."

Celty nodded and grabbed Shizuo's arm, pointing at the door. The blonde, who had just realized with horror what he had done, got up slowly and exited like a dog who knew he had done something wrong. The dullahan then went over to Izaya and lifted him up so he could balance on her shoulder so she could help him walk out.

Shizuo was already sitting on the couch, holding his head and shaking. He… he wanted so much to kill Izaya but he knew he could never do it. If he did, he would be at the same level as the damn informant… or worse. What he had just done, or what he had almost done, frightened him to no end. He looked up as Celty led Izaya in, the dullahan setting the weak informant on the couch.

'Okay,' Celty typed on her PDA. 'What happened in there?'

"Isn't it obvious?" Izaya snorted. "Shizuo tried to murder me."

Shizuo flinched. Izaya wasn't referring to him as Shizu-chan anymore.

'I bet you gave him good reason,' Celty typed again. If there was one thing she knew about Izaya, it was that he was an insensitive asshole. Therefore, she wouldn't be surprised if Shizuo had attacked the informant for saying something hurtful.

Izaya pouted and glared at Shizuo. True, he had given him good reason. "I was just teasing again…"

Celty shook her head (or lack thereof) and wondered if this was what elementary school teachers had to deal with. 'You know Shizuo can only take so much. You were probably skating on thin ice again.'

Shizuo looked at the ground, feeling slightly ashamed. True, it was partly (meaning mainly) Izaya's fault but it was too kind of Celty to stand up for the blonde. Shizuo had almost murdered Izaya in cold blood and he felt like he shouldn't be let off so easily.

Before anymore could be discussed, Shinra exited the lab, firmly closing the door behind him. He walked over to the group and flopped onto the couch with a sigh.

"That's going to be a lot of work…" he sighed and then looked at everyone else. "No one should go in there without breathing protection until I'm done cleaning. All of those chemicals mixed together could produce fumes that could cause just about anything." He frowned at Izaya and Shizuo. "How much did you get on you?"

"Well, seeing as Shizuo threw me into a giant puddle and then more broke on top of us… I would say quite a bit," Izaya said.

"I should warn you now, I haven't tested most of those," Shinra said with a serious expression. "There might be some highly unnatural and strange side-effects."

"Shinra, I will beat your face in if I get turned into a girl or somehow get pregnant," Izaya glared at the doctor. "Or both."

"It's just a warning," Shinra said. "I don't even know if the chemicals mixed together just canceled each other out. For all I know, nothing will happen. But I'm not sure about that so I'm warning you two that something might."

Shizuo frowned. "What should we do if something does happen?"

"Come here and let me know," Shinra said. "I'll try and test what's left of the chemicals to see how they interact and, if possible, make an antidote. For now, you two should just go home and get some rest."

"Sounds good to me," Izaya said, getting up and stretching. "I'm tired all of a sudden. Probably because of all the running around I did today." He headed for the door and waved, his smirk now on his face. "Ja nee!"

Shinra shook his head and got up. "Well, I have to continue cleaning up. I'll see you later, Shizuo."

The blonde on the couch sighed and hung his head. Celty suddenly felt concerned and typed a message on her PDA.

'Shizuo, are you okay?'

Shizuo shook his head. "I almost killed him. I almost murdered him. I was just so mad… I didn't know what I was doing…" He stared at his shaking hands. They held so much power… they were so destructive. Maybe Izaya was right… maybe he was a monster…

'Shizuo…' Celty began and erased the text, trying to figure out something else to say. She actually had no idea what to say. Besides, what could she say? "It's going to be okay?" It wouldn't work.

"I… I should go…" Shizuo sighed, pushing himself up from the couch. "I'll see you later Celty…"

The dullahan nodded and typed, 'Goodbye.'

The blonde left, closing the door softly behind him and began his long walk back home.

…

"Namie!" Izaya called out when he reached his apartment. Usually, he didn't feel so drained when he got back to Shinjuku. He just felt so tired all of a sudden. "Namie! Where are you?"

"I'm coming," Namie Yagiri snorted as she walked down the stairs of the loft. "What do you want now?"

"Cancel all appointments I've made for today," Izaya muttered as he flopped down on the couch. "I'm too tired to deal with anyone right now."

"As long as I get to leave early," Namie sighed, knowing full well that she would have the day off if Izaya was out of commission.

"Fine, fine…" the informant said, waving his hand lazily from the couch. "Just make sure no one disturbs me…"

"Whatever."

Izaya grabbed a pillow and buried his head in it, happy to be stationary and stretched across a soft surface. Content, the informant drifted off to sleep in no time and Namie had to resist scribbling on his face with a sharpie.

…

"Shizuo, I think you should go home for the day," Tom sighed, noticing that his bodyguard was nodding off again.

"Eh? Wha…?" Shizuo mumbled, his mind foggy and tired.

"You look like you haven't gotten any sleep," Tom said with a frown. "Are you sure you're okay?"

"I'm fine, Tom," Shizuo protested, pushing his sunglasses up and stifling a yawn. "Just… fine…"

Before he knew what was happening, Shizuo felt his knees buckle and he collapsed, falling to the ground with little grace.

"Shizuo!" Tom gasped, rolling his friend over to see if he was okay. After examining the blonde, Tom decided that Shizuo was just exhausted and needed some rest.

So the debt collector called it a day and dragged Shizuo back to his apartment, laying the blonde in bed. Tom gently set Shizuo's shoes and sunglasses aside and turned to leave.

"Rest up," he said to Shizuo's sleeping form. "I'll see you tomorrow."

With that, Tom left the apartment before seeing the blonde roll over in his sleep, a look of discomfort on the man's face. The expression was gone fast and was slowly replaced by a content smile.

Little did Ikebukuro know that the next morning, the city would be in for a surprise.