A/N – Whoo! This chapter fought me at every turn, but finally, after 84 years, we have the mission that ended up with Obito graciously giving (read: stubbornly throwing) his eye to Kakashi.

"These fuckers just won't go away! What the fuck is up with them!?" Obito whined as he and Kakashi ran back from Iwa.

The nuke-nins (officially. Unofficially the mission was a covert operation against Iwa) they had been targeting had followed them into Kusagakure. Kakashi had sent the information they needed (a Kinjutsu Iwa had stolen from Kiri, which had in turn been stolen from Iwa by them) ahead with Pakkun already, and he would have it with Minato soon enough. Backup may or may not arrive, but could not be relied upon.

He felt the ground moving under him, and quickly moved chakra to his feet to jump over the cracking earth. He could hear Obito following behind him, cursing.

"Will you shut up!? They can hear you all the way in Konoha!" Kakashi snapped at him, trying to keep his voice from carrying beyond Obito (doing that was always a risk, since Obito was empty-headed at the best of times and he had been worse after Rin had agreed to date him. If the Iwa shinobi heard him but Obito didn't, Kakashi was just going to leave him here). The shinobi were getting closer, and he would prefer to not have to fight 5 of them with an idiot to look after.

"Great!" Obito jumped over a boulder that broke out of the earth, looking back and throwing a fireball into the distance. There was a scream. "Then they'll know we're on our way and send someone more helpful than you, Bakashi!"

'Moron!'

Kakashi smelled charred flesh. One down, probably. But they can't be sure.

He skidded to a stop when a shinobi materialised in front of him, throwing a kunai at him. Kakashi dodged, throwing a kunai back, which was also dodged.

Another flew at him with a chigiri, aiming for his legs. Kakashi quickly pulled back, and sent a Lightning Dragon towards them.

Both of them were electrocuted, and Kakashi hoped that they would stay down.

He turned and saw Obito fighting another shinobi, listing to the side.

'That Idiot, he got stabbed already?'

Kakashi was about to turn to his own two (maybe Obito did get the one from before) when he saw another shinobi creeping up behind Obito.

He quickly looked to the side. The two he had electrocuted didn't seem like they would get up anytime soon.

Kakashi ran towards Obito as the other shinobi pulled out a kunai.

_

Obito pulled his kunai from the downed shinobi. As he was readjusting his grip, he heard grass crunching under feet, far too close for comfort.

Obito turned around, and fell back as the shinobi slashed at him with a kunai. He grunted at the miss, and swung down to stab Obito.

Obito swore. He heard the sound of chirping birds that was cut off abruptly, followed by a pained grunt.

But...

'Nothing hurts? Only my side... Where...'

Obito looked up to see Kakashi in front of him. The sounds of pain were coming from him.

"Bakashi..."

Kakashi grabbed the shinobi, deflecting his kunai with his own, and pushed lightning chakra through him, electrocuting him. The shinobi was stunned, and Kakashi stabbed him through the heart.

Obito stood up, and instead of going to Kakashi as was his instinct, took stock of the situation around him.

All the Iwa shinobi were down.

Both Obito and Kakashi checked the vitals of the downed shinobi (Obito more than Kakashi). The two Kakashi had electrocuted were still clinging to life, and were dispatched by Obito with a kunai to the chest.

Once that was done, Obito pushed Kakashi to sit down under a tree, and stacked the bodies in one place, incinerating them beyond recognition with a couple of fireballs.

When their remains were found, it would be a hard sell that they were killed by Kiri shinobi, given the fire jutsu being used. Nevertheless, even if they blamed Konoha, they wouldn't have any evidence to make any concrete accusations.

Obito rubbed at his eyes.

They felt... weird...

Everything seemed sharper and slower than before...

'... No fucking way!'

His Sharingan!

He finally had it!

Obito felt strangely tired, but didn't give it too much thought. The mission was tough and they were both injured, exhaustion was expected. He was much more focused on his Sharingan and where he would take Rin for their first date.

After years and years (and years) Rin had finally agreed to go on a date with him, and he was not going to let getting stabbed, of all things, ruin it for him.

Obito saw Kakashi's bloody face, and immediately all thoughts of the date went out of his head as he remembered what had happened.

'Focus, Obito! Date later, first we get Bakashi back home!'

"Oi, Bakashi!" Obito sat next to Kakashi, whose hand was covering his left eye. He put a hand on his shoulder and shook him a little. "Are you – "

"Let's go. We need to get back." Kakashi winced in pain as he stood up, shrugging Obito's hand off. He couldn't see anything from one eye, and the other refused to open from the pain. He tried to smell anything beyond the smoke and copious amounts of blood, both his own and the Iwa shinobis', to no avail.

"Right, fuck! Let's... go..." Obito stood up after him, swaying in place. His hand pressed the stab-wound in his side. He felt fire running through his side, and looked down to see if he had accidentally burned himself (it would be far from the first time that had happened).

There was just blood.

"Oi, Obito?" Kakashi grumbled, trying to smell if something was wrong. Again, the scent of blood was strong everywhere. He snapped at him, "Obito! What happened!?"

Obito tried to pull everything Rin had told him about medical self-assessment to the forefront (unfortunately, he had been too busy gazing at her beauty to remember all of it. Fortunately, he always paid extra attention when Rin spoke, which thankfully had a net positive effect).

His side is burning, but he didn't burn himself. Dizziness, pain (mostly because of the stab-wound. Probably).

Was his heart stuttering?

"Obito!"

"P-Poison..."

_

"Fuck!" Kakashi swore, and performed a quick summoning. As he propped Obito up, Urushi and Bull popped up in a cloud of smoke.

"Urushi, Bull, I need you to reverse summon us to Konoha Hospital." Kakashi commanded, adjusting Obito's weight and trying not to fall on his ass.

"Got it!" Urushi and Bull affirmed. Bull came up to him. "I'll take Obito."

Kakashi nodded, then shook Obito to get his attention.

"Oi, Obito! Wake up, moron!"

"Whaddaya want..." Obito groaned, panting harshly. Kakashi still couldn't smell any poison, let alone what was in it, because of all the fucking blood!

"Hold onto Bull, okay? We're getting you back to Konoha." Kakashi grabbed his listless hand and guided it to Bull's collar. "Hold on tight."

"Whabout you..."

"I'll come with Urushi." Kakashi snapped quickly, trying to push down the panic bubbling up. Obito's fingers were turning blue already.

He stumbled his way to Urushi, who closed in the distance and brushed closer to Kakashi's hand, making it easier for him to grab onto him.

"Let's go!"

_

Rin was on her way to the canteen for her break.

Learning medical Ninjutsu from Tsunade was simultaneously the most fulfilling and the most tiring thing that had happened to her, even though she refused to actually perform any procedures and only gave theoretical lectures.

It was fulfilling because she was contributing to saving lives and helping people, and tiring because the more she learned, the more it was clear that she didn't know much at all. She nodded at a fellow intern when she heard a shout.

"Rin!"

'Kakashi-kun?'

Rin quickly made her way to where the shout came from – 'the entrance, they just got back. Something must have gone wrong with the mission' – and forcefully pushed down nausea at the sight before her.

Kakashi's face was covered in blood – 'Injury? Laceration to the eye. Possibility for infection, he's going to need a prosthetic eye' – and he was holding onto Urushi, who was seated on the floor (quite impatiently, he looked like a treat was being withheld from him) and glaring at the receptionist (who was not a dog person in the worst way).

She moved her observation onto –

'Oh, Obito-kun!'

Obito was slumped over Bull, breathing heavily. Rin ran over to them, and signalled Kimiko for two stretchers after requesting her to alert Ayasa.

She pushed down all panic and gingerly examined Obito. 'Stab wound to the side. Heavy bleeding, Oh Kami, there is so much blood!' "What happened?"

"He got stabbed. 5-10 minutes ago. There was poison on the weapon." Kakashi ratted off, shaking his head and glaring at Takahiro, who was trying to get a look at his eye. "He got dizzy pretty fast."

"Hatake, will you be still for a minute?" Takahiro did a good job seeming like he didn't want to strangle Kakashi for making his job harder. "I need to check your eye."

"I'm fine." Kakashi mulishly griped. "You know what's wrong with him?"

Kimiko and Hiroyuki came by with a stretcher that they placed Obito on. Nobuki and Shūsuke had the other stretcher, watching as a harried Takahiro tried to convince Kakashi to get onto it.

They were placed in Ward 12, and the curtains were pulled out to seperate the two beds. Just as Rin steeled herself to attend to Obito, Ayasa came flying through the doors, her brown hair shoved into a cap, grey eyes piercing as she took in the patient.

"Status report!" She barked, pulling on gloves.

"Stab wound to the side. Poisoned weapon, not sure what poison it is. Known symptoms were dizziness and – " Rin quickly rattled off, interrupted by a pained groan. Obito mumbled something.

"What was that, Obito?" Ayasa asked, voice gentling as she lightly pressed her fingers around the wound.

"B-Burns... Heart f-feels..." Obito stammered hoarsely, wincing as the words scraped out of his throat.

"Burns, Obito?" Ayasa asked, running an eye over him again. "You don't have any burns."

"F-Feels like it." Obito tried to smile, although it came off as a grimace. "Heart... Heart feels..."

"Yes, Obito?" Ayasa looked at Rin and gestured at Obito's hands. Rin grabbed a hand and examined it. His fingernails were entirely black, and his fingertips were on their way as well.

Rin heard an 'I see' in a pinched voice, and looked up to see Obito's hand come down from a sign that had her heart in her throat.

Halt

'Heart palpitations'

Rin felt her eyes burning, and immediately tried to push everything to the back of her mind. She needed to see this through. Ayasa would already try to get her to leave after he was stabilized, given how close she was to both the patients. She wouldn't risk Obito's life because of panic.

That could come after he was okay and recovering, planning to take her on their first date.

_

Rin was very close to panicking.

It was early the next day, and Obito had been stabilized, although the situation was still precarious. The poison was still in his body, and since it didn't seem to be any common poison, a blood sample had been sent to figure out what it was. Given that the results still hadn't come back, Rin was getting more and more worried that it would be something they didn't have an antidote for.

She had also been correct that Ayasa wouldn't allow her to take on either of their cases in any capacity. She had, thus, had to distract herself by visiting other patients.

Rin wished that Tsunade was here to help, but she and Shizune were in Hachō Village, helping with a sickness that had spread quickly through the villagers, with no concrete date for their return.

Kakashi was doing better, but not by much. The loss of his eye would take a while to get used to, and his depth perception was shot to Hell. Having Sakumo there helped, but he was also worried about Obito, much as he tried to hide it.

Rin quickly chugged a cup of strong (and terrible) coffee, barely registering the burn.

"Rin."

"Senpai." Rin turned and made her way to Ayasa, who was frowning down at a clipboard. Rin felt a cold stone drop in her stomach. "Did we get Obito-kun's blood report back?"

"We did..." Ayasa drawled, then sighed, looking at Rin a little pitifully.

"Rin," Ayasa sat her down, fidgeting with the clipboard in her hand. She pressed her lips together thoughtfully. "Normally I would not bring this up with you, but..."

The stone in Rin's belly was getting heavier and heavier.

"Senpai, please tell me, what poison is it?"

Ayasa took Rin's hands between hers, and squeezed. As things were, Rin felt no comfort.

"We don't know." Ayasa grimaced, her fingers tapping on the back on Rin's hand. "It's not one we've come across before."

Rin felt as if the floor had given way under her, and she would have fallen if she were not sitting (she felt like she would fall regardless).

"We don't – " Rin's voice was breaking miserably. "T-Then – "

"We'll try to keep him stabilized till Tsunade-shishō gets back." Ayasa gave her a smile that fell flat. "She will be able to make the antidote, but..."

But whether Obito would live that long was up in the air.

_

Rin and Kakashi sat at Obito's bedside, all three trying not to bring the mood down with how miserable they were feeling. After two days, Tsunade had still not returned, and it was getting harder and harder for Ayasa to keep him stable.

Minato had sent a message for Tsunade to return, but it was unclear whether it reached her or not. And even if it had, it would still take her a while to actually get back here.

Obito's grandmother, Uchiha Rei, had come to the hospital almost immediately upon being informed, and had stayed by Obito's bedside the whole time, followed soon after by Sakumo, who posted himself by Kakashi's bedside. Uchiha Fugaku and Mikoto had showed up the day after, and he and Rei had had a long talk with Obito that they had insisted was a clan matter, during which Sakumo and Kakashi had left for a walk to give them privacy (everyone had very politely not brought attention to Kakashi bumping into the doorframe, both on his way out and back in).

Rei had just left the room, looking grim, going outside to speak with Sakumo, who had just brought some lunch for Kakashi (who had taken to staring out of the window towards the Village gates with single-minded determination, as if he could glare Tsunade into existence).

"Rin-chan, I'm sorry I couldn't take you on that date." Obito grinned at her weakly. Rin quickly wiped her eyes and held his hand by the wrist, trying to avoid the blackened areas.

"You'll get to, Obito-kun." She nodded firmly, her voice breaking as she spoke. "Tsunade-sama will get you better and we'll go on that date and I'll order the most expensive things I can!"

"I'll hold you to that, Rin-chan." Obito laughed hoarsely, and looked at her with so much affection that she almost broke down into distraught sobs. His breath was harsh and laborious in his chest, and he was silent for a while. "Oi... Bakashi?"

"What?" He asked without turning from his lookout.

"When I die – "

"Oi!"

"Obito-kun!"

Obito waved a weak hand at them, asking them to quiet down. "Rin-chan, I appreciate everything... you and Date-san have done for me, I really do... but all of us know, we will need a miracle for me to live."

He showed his fingers, which had turned fully black. Black veins were running up his arms, which both Rin and Kakashi had been trying to ignore as much as possible.

"Just... just let me say this... okay?" Obito pleaded with them.

Rin hung her head tearfully, nodding shakily. Kakashi wound up to disagree again, but was silenced by Rin's glare, rare as it was. He exhaled loudly, gritting his teeth, and nodded back.

"When I die," Obito began, licking his cracked lips. "I... I would like for Kakashi to have my eye. He lost his, trying to keep me alive. It's only fair."

Obito turned his head to look at Kakashi. "I would like to... I would like to see the future with you."

There was a silence as both Kakashi and Rin digested that.

'Oh, Obito-kun...' Rin's vision was blurred by her tears, and her chest heaved with quiet sobs, but she was jolted out of her sorrow by Kakashi's loud scoff.

"Absolutely not! Are you out of your fucking mind!?" He yelled, standing up from his bed and coming up to Obito's bedside. He gripped the sheets furiously, looking like he wanted to be gripping Obito's neck instead. "What's next? I go on a date with Rin for you?"

His yelling brought Sakumo and Rei rushing back in, and Sakumo grabbed his son and deposited him back on his bed.

"I'm not taking your fucking eye, you moron! You think I jumped in front of you just for you to die!?" Kakashi angrily vibrated in place, being held back by his father. "You want me to take your fucking eye, you shove it in my head yourself, you hear me!? You survive, get better, and force that eye in, if you want me to have it! You – "

"Pup, that's enough!" Sakumo held him by the scruff of his neck and shook him a little. He shot an apologetic look at Rei, mixed with a healthy amount of concern. "Calm down, okay? Obito's already not well, don't yell at him."

"Tou-san! You don't know what that idiot said!" Kakashi looked back at Sakumo, pointing at Obito again.

"Kakashi! Enough!"

Kakashi glared mulishly at everyone in the room, silently fuming with his crossed arms. He viciously kicked the bed he was sitting on, once.

Obito seemed torn between laughing (painfully) and wincing (also painfully) at Kakashi's outburst.

As Rei came close to return to her grandson's bedside, Rin decided to do some damage control.

"Obā-san, I am so sorry!" She bowed her head low and nervously smiled at Rei. "Kakashi-kun is just worried, as am I, and Sensei too. He didn't mean it."

Rei just smiled at her serenely, the smile itself not reaching her bloodshot eyes. It was heart-breaking to think that the woman might lose the only family she had left.

"I understand, Rin-chan." She quietly reassured her, pointedly not looking back at Kakashi and Sakumo, who were whispering among themselves, lowly but furiously. She ran a trembling hand over Obito's feverish forehead. "Obito-kun has called him an idiot enough times as well. It cancels out, I think."

"He deserves it." Obito quipped tiredly, the excitement apparently draining his energy. "Obā-san – "

"Rest, my dear." She gently rubbed her thumb over his brow and kissed his forehead. "Tsunade-sama will be here when you wake up. I promise."

_

Tsunade and Shizune were within sight of the Village gates, and they quickly signed their names into the register and dashed towards the hospital.

Minato had sent a missive two days ago, asking them to return urgently. Since most of the important work had already been done, she left care instructions with the nurses at Hachō Village and they rushed back to Konoha. The nurses would not be enough, but there were volunteers who could take quite a bit of work off of their hands, leaving them free (relatively) for the actual healing.

The message had said that Obito, one of Minato's brats, had been poisoned by some novel poison on a mission in Iwa. She didn't have all the details. Firstly, because the blood test had mostly likely not returned when the message had been sent. Secondly, because she was sure Minato would know that she would leave immediately, which made sending a copy of the report moot since it wouldn't reach her anyway.

"Bring me Ayasa!" Tsunade burst through the doors of the hospital, yelling at the receptionist. "Uchiha Obito, room number!"

The girl squeaked and quickly sent for Ayasa, knocking papers off of her desk in her haste.

"Ward 12!" She yelped from below the desk as she picked up the papers.

Tsunade made her way to the east wing where the room was, Shizune jogging after her hurriedly. Ayasa joined her halfway through and gave a succinct report.

Immediate symptoms: Dizziness, burning in the wound that the poison was administered through, heart palpitations.

By the end of the first day: blackening of fingernails and fingertips, shortness of breath.

Second day: blackening spreading up the arms, fever, chakra fluctuations and heart palpitations continuing throughout.

The poison was plant-based and spreading through the blood. It didn't attack the entire nervous system (small mercies), but what it was doing wasn't any better.

They were having trouble in terms of making the antidote. A lot of ingredients were counteracting, which made her think there was a binder that was holding them together and allowing it to work like it was.

"We've been keeping him stable, but the poison's been fighting us." Ayasa ended her report, handing her the lab reports on what they knew about the poison and pushing open the door to the room.

Uchiha Rei, Hatake Sakumo and Hatake Kakashi looked up at her as she entered (the boy was down one eye, what kind of mission were they on?). Rei stood up to move away, but Tsunade gestured for her to remain seated.

Tsunade, Ayasa and Shizune surrounded the bed, looking at one Uchiha Obito who definitely looked the part of a poisoning victim.

There were black veins crawling up his arms, his hands and fingernails entirely black. He was burning up with a high fever, and his eyeballs were moving behind his eyelids frantically. Tsunade grabbed a stethoscope from Ayasa and checked his heartbeat. Erratic, with up to a few seconds of pauses between them.

Clearly the medical stasis was not an option anymore.

Tsunade lifted up his eyelids to check his eyes. "When was he last awake?"

"Yesterday afternoon." Rei answered her with a voice heavy with worry. "He hasn't woken up since."

"Hmm."

His Sharingan was active, two tomoe spinning. Tsunade reached out to sense his chakra, and found out that it was draining far faster than she would have expected it to if his body was trying to heal itself.

'The poison affected the Dōjutsu and activated it to move the chakra away from healing? But what could do that?'

"Was his Sharingan active when he was last awake?" She asked, examining the black veins on his arm. It looked necrotic, but didn't feel that way? She moved the sheet up to check his feet. No discoloration.

'Strange'

"No, no." Rei looked at Obito worriedly, turning back to Tsunade a little frantically. "Is it active?"

"It is." Tsunade pushed healing chakra to her palms and dove in, trying to figure out how best to increase his stability to give her time to create the antidote. "Shizune!"

"Yes, Shishō!" Shizune snapped to attention. "Dizziness, paresthesia and ventricular arrhythmia, difficulty breathing. Possibly wolfsbane?"

"No neurological affects."

"The Sharingan is active, so it must be traveling through the chakra network." Shizune observed as Tsunade healed Obito. Some of the black veins moved back, but not entirely. So, not necrosis. "It could be mixed with ambervine."

"Possibly."

'It would be so helpful right about now, to have the Byakugan.' Shizune thought to herself.

After a grueling 40 minutes or so, Obito was finally as stable as Ayasa had him on his first day at the hospital. The poison was still in his system though, and it was best to quickly flush it out before it got more stubborn.

"Ayasa, keep me updated." Tsunade pushed back some strands of hair that had fallen over her forehead, wiping the sweat off of her brow.

"Will do, Shishō."

_

It had taken a nail biting couple weeks of stabilising Obito and testing antidotes on blood samples taken from him before Obito was actually, fully stable. It took another fortnight of watching for side-effects of the antidote or remnants of the poison before Obito was finally discharged from the hospital.

Things had gone pretty much back to normal, since then.

Sakumo had taken Kakashi to the hospital to get fitted for his prosthetic eye (he would have gotten it sooner, but his eye got infected because someone was too busy yelling at his bedridden teammate for having a dying wish to take care of his own injury), and he was reviewing some scrolls in his study while Kakashi rested in his room when there was a commotion at the front door.

"Oi, Bakashi!"

Sakumo held back a chuckle, putting down the scroll as Obito came bounding in, peeking through the doorway and waving at him enthusiastically. It was nice to see that almost dying hadn't dampened Obito's spirits for long (his second date with Rin yesterday may have also helped).

"Morning, Obito." Sakumo greeted him with a grin, calling after him as he went off. "What brings you here?"

"It's time for me to fulfil Bakashi's wish!" Obito yelled back. There was silence for a moment, then a loud 'what?', followed by the sound of feet running.

'Oh, fuck!'

Sakumo heard a floorboard squeak and a door slam open.

'The courtyard. Kakashi's pulling a runner'

Of course this is how Obito breaks the news of Kakashi's upcoming eye transplant.

Sakumo knew that his son was hoping that Obito would forget about it (or as he said, 'that idiot will come to his senses after some fresh air outside the hospital'), and Sakumo won't lie, he had hoped so as well.

Clans with Dōjutsu were notoriously brutal about keeping their eyes within the clan, and giving someone your eye was a very significant gesture when you were dead, let alone when you were still alive.

Fugaku had tentatively agreed to let Kakashi have Obito's eye when he was in danger of dying, but it was highly likely that he would retract his permission now that Obito was alive and well.

Or at least, Sakumo had thought so.

"Get the fuck away from me!"

Sakumo sighed.

Time to go and make sure his son didn't take out Obito's eye (or, Kami forbid, his own remaining one).

A/N – I think it goes without saying, I know nothing about poisons.

This chapter was so tricky, especially since I had to figure out the Medic Corps during what would have been the Third War.

In the first draft Obito was supposed to get worse while they traveled back to Konoha, but it seemed almost too easy. I thought to myself 'Yeah, the stakes would be high if it took them time to get back because Kakashi's pack can't reverse summon them to Konoha, but what if they can!' Then there was the issue of how exactly Kakashi would get his eye. Rin could transplant it while Obito was still alive, but she would definitely lose her license because of it, which I didn't want. And so we ended up with this.

Kakashi is 13, Obito and Rin are 18.

Also, for everyone wondering why Kakashi was like that, it's because

1. He's 13

2. He is, at his core, Sasuke but 5 inches to the left

3. He's 13!

Tsunade and Shizune didn't leave Konoha, although Tsunade did develop Haemophobia and give up actually treating people at the hospital. She still gives theoretical lectures, but for the practicals you have to shadow someone else. Shizune is her apprentice who shadows her. Date Ayasa is a character I made up (along with most of the people in this chapter) and she is the Head of the Medical Corps. I also gave Obito's grandmother the name of Uchiha Rei.

Also, it just came to my attention that Sakumo fought in the Second War, not the Third, so he should've been dead, but we'll keep things as they are. This story is already off the rails.

Let me know what you think!