In the dark of the cave, Rin can't see Obito's eyes or his face but she can hear him clearly, the small, fearful hitches of his breath coming in staccato. He's kneeling by the boulder, head bowed, holding onto the limp hand like it's a port in a storm.
"Kakashi," Obito begs. "Kakashi, wake up."
Their teammate stirs, and something twists sharply in Rin's gut.
She had hoped he had already gone. She had hoped that he hadn't felt it.
"Obito?" Kakashi murmurs distantly. He tries to turn his head, and can't. It sounds like there's something wet at the back of his throat.
"I can't - I can't see you, Obito." There's fear in his voice, edged by an even more uncharacteristic panic. "Where are you? Where's Rin?"
It's only then that Rin notices the red-tinged clear liquid seeping out from underneath Kakashi's single uncovered eyelid, how it dribbles thickly down his face and pools darkly where it meets the navy blue cloth of his face mask.
Her heart sinks.
She reaches out, curls her fingers around his arm. "We're here," Rin says clearly, calmly, because she refuses to let Kakashi hear even a bit of the fear and horror that has begun to take up leaden weight in her gut. "We're right here, and we're not leaving."
He sags in relief at her touch, sharp-edged hysteria smoothing out into something unfairly soft.
"It's - it's so dark, Rin," he says, and she flinches.
Kakashi sounds terrified and small, in a way that she just can't associate with the aloof genius she had called her teammate for so long. For the first time, Rin remembers that he is younger than her and Obito. Not by much, just a few years, but now it felt like everything.
"It's okay," Rin says, even though it's really, really not. "It's okay, we're here with you."
It's the wrong thing to say, she realizes later with the perfect vision of hindsight. Because Kakashi stills, and even though between the rock and the mask just a sliver of his expression is visible, she thinks she can see a terrible sort of understanding bloom over his face.
"...It's not dark, is it?" Kakashi says dully. " I'm blind." He's quiet for a moment. "I'm dying."
She squeezes his arm, and it's the only reply she can bring herself to give.
"It's my fault," Obito says suddenly, his voice choked. He curls into Kakashi's limp hand like it's a gut wound. "I made you come back. You were gonna go and finish the mission like we were supposed to, but instead you came back and lost your eye to save me. And now, you're -"
Kakashi is all soft voice and disdain, even through the pain.
"Do you really think you can make me do anything?" He says flatly. "I chose to come back, Obito. I chose this."
They're quiet for a moment, all three of them.
"But it shouldn't have been you," Obito whispers, voice small. "It can't have been you, Kakashi. It's not fair. You're the genius, you're the one everyone calls the best of our generation, you were supposed to survive everything and become a legend just like the White Fang!"
The smile Kakashi gives through his mask is almost a grimace. "Then I guess," he says, and wheezes in another weak breath. "I guess those are your shoes to fill now, Obito."
A strange shudder goes through Obito at those words. His expression goes terrifyingly blank. Rin sees it all even though Kakashi does not, and she knows in a way she cannot explain that something has gone terribly wrong.
"You should go," Kakashi says quietly, and Rin recognizes his forced, false calm like she's looking into a mirror. "Our enemies have back-up coming, and they'll be here any moment. You know that."
"So leave me."
"I can't," Obito says dully. He doesn't, can't look Rin in the eyes.
Kakashi lets out a slow breath. "Obito," he says. "I saved your life, right? That means in some sense, it's mine. You owe me."
"Yeah," Obito says, hiccuping. "Yeah, Bakashi."
"Then go," Kakashi says with an intensity Rin doesn't think he could still muster. "Because I want you to take my blade with you, and carry on that legacy. I can't do it myself, so you have to do it for me."
Obito is quiet for a long moment before he says, something strange and distant in his voice, "Okay."
Then, "But you have to take my eye."
Rin jolts, looks between the two of them like she can find her answer there.
"I never gave you a gift for your promotion," Obito says, looking up for the first time, and his eyes are the red red red of the Sharingan but the dark pattern in them is something she has never seen before. They're shining with tears.
"I won't leave you in the dark, Kakashi."
"If you give me your eye," Kakashi says slowly, carefully, like he's testing the words, "you'll never reach your full potential. You'll never be as strong as you would be with both your Sharingan. You know that."
Obito doesn't hesitate for even a second. "You didn't need the Sharingan to be great. I won't either."
And then he says, before Kakashi can protest again, "Please. Let me see the future for you, Kakashi. Even if that's into the afterlife."
The sharp shock in Kakashi's expression softens into an emotion that Rin cannot describe with words.
"Alright," he says at last. "Alright, Obito."
The operation takes forty-five minutes from beginning to end.
Rin's hands shake only once.
When they leave Kakashi behind, they feel the weight of his new Sharingan on their backs until the very end.