Disclaimer: I don't own the Naruto-verse or any of the following characters.
He ran, ignoring the ache of his weak old body. He dashed through the trees, ignoring the pain. He had to find an Uchiha, a new body, and fast. He could already feel this body failing him, but he refused to release it. He refused to disappear.
He came upon a pile of rocks, clearly a recently caved-in cave. He was about to continue, but noticed that there was someone underneath the rocks, someone still alive. He moved the rocks, optimistically assuming find he'll find what he seeks (in reality he was hoping, but he'd never admit that, not even to himself). He was not disappointed. A young, dying Uchiha, his right side almost completely crushed and his left eye missing. Most medics would decree him beyond help, a dead man. But not him.
Using what little life remained in this old body of his, he repaired the boy's injuries. He would still be deformed, but that didn't matter to him, this body will still function well, and had a new Sharingan eye, and that was all that mattered.
The boy's single eye opened, and he looked upon his saviour. "Who- who are you?" He rasped, barely able to form the words with his deformed face.
The old man didn't answer; instead he stared into the boy's eye, his Sharingan spinning to life, activating the boy's own. They stared into each other's eyes for a few seconds, before the old man crumbled. Before his body could hit the ground, the young boy caught it. The boy's face was split by a mad, evil grin as he laid the old man's body on the ground, and reached for his left Sharingan.
"You have served me well, and your eye shall serve me a little longer." He said.
The battle field is a nightmarish place, bodies and weapons strewn about, blood soaking everything, and the cries of the wounded and dying echo through the air. Rin tried to ignore the battle raging behind her, and tried to concentrate on healing the man in front of her. After a short while, she stopped. No point in continuing to heal a dead man. She got up and began to search for her next patient when she saw him.
He wore the same clothes as when she last saw him on that day, although his goggles were missing. Both his eyes, red spinning Sharingan, sparkled with glee when he laid eyes on her. He began to walk towards her, but she was too shocked to react. It couldn't be real, it had to be a dream, or a Genjutsu spawned lie, it just couldn't be real.
Obito Uchiha was dead, and even if he was alive, he would only have one eye, since he had given his left eye to Kakashi. She had done the operation herself!
"Hello, Rin" Yet here he was, calling her name. His right side looked deformed, but he could still moved, as if it hadn't been completely crushed by several tonnes of rock.
"Obito" She whispered, finally managing to get her lips to work as she gazed into his eyes. "What are you doing here? How are you still alive? And with two eyes, nonetheless!?" She screamed, all of the pent up feeling since his death coming out in a torrent emotion. She couldn't believe he was here, yet she'd already tried to dispel the illusion to no effect...
"I need something, Rin, before I go and truly disappear." He said, looking at her almost sadly. He was acting rather calm and generally un-Obito like, but she couldn't seem to care, or move. He brought his hand to her face, gently caressing her cheek and tucking a lock of her brown hair behind her ear, and gave her a gentle smile.
She tried to return it, but the smile turned into a shocked gasp as pain exploded in her abdomen, she looked down at the kunai sticking out of her, and the hand attached to it. "Obito" She gasped out, blood pooling out of her mouth."Why?"
He smiled, a cold, evil smile that had no business being on her dead teammate's face. "I told you I needed something" He said, the pleasure all too obvious in his voice as she crumpled to the ground. "I needed the Mangekyou Sharingan, and killing you was the easiest way to get it." Giving her another smile, he crouched down next to her. "Wanna know a secret?" He asked, still with that ridiculously amused evil smile. He leaned so he could whisper in her ear. "I'm not Obito; I just took over his body. But your death will still awaken his Mangekyou. Farewell, Rin."
With those last words, his eyes morphed into their Mangekyou form, and he used his newly acquired space-time jutsu to transport himself to his secret base. There waited for him his loyal companion, Zetsu.
"Welcome home, Tobi."