Obito's eye stares back at Sakumo from Kakashi's drawn face. The single black tomoe spins slowly against a deep ruby iris, a full drop of crimson welling slowly against Kakashi's pale lashes. He blinks and the lashes cling together before reluctantly separating into blood-sticky strands again.
"Are you all alright?" Minato pants as he hurries over, his clothes and skin gore-splattered. "Where's—" His throat closes around the question as he comes to a stop before Kakashi. The Sharingan stares up at him, still spinning-spinning-spinning.
Kakashi closes the eye and cups a shaking hand over it.
"He saved me." He pauses, swallows. Steadies his voice. "We were about to leave the cave when the enemy collapsed the ceiling on us. He pushed me out of the way... and a boulder got him." Kakashi's deliberate report-like tone does nothing to ease the shock that strikes through Sakumo like a bolt of lightning.
A strangled sound escaped from Rin's throat and her fingers tighten spasmodically around Kakashi's wrist. Sakumo dazedly tracks the movement, moving up, up, up until he reaches the look of utter desolation that had etched itself onto Kakashi's face. Sighing lowly, Minato folds them both into the comfort of a tight, brief embrace, his hair seeming to dull with his deeply sorrowful expression.
If not for Obito...
At the thought of his son being the one trapped under that boulder, his body crushed beneath heavy stone, Sakumo heart palpitates against the hollow of his throat. Seeing Kakashi so wonderfully alive and whole makes the terror of almost having lost him multiply tenfold.
Seized with an irrepressible reflex of relief, Sakumo turns grateful eyes towards the crumbled entrance of the cave. Yet a moment later he is awash with guilt for feeling this way.
Obito is someone's beloved son as well. Someone else's precious child who had traded his life for his Kakashi's.
Breathing shallowly, Sakumo approaches the pile of rocks that seals the cave's entrance. Phasing through the heavy boulders is simple if uncomfortable, but Sakumo stops once he is within the cave, unable to take another step forward.
The darkness is complete. Not a stray beam of light manages to illuminate the cold, dusty space. Sakumo can hardly accept that Obito, a boy who had only minutes ago brimmed so full of life, is lying dead and still in this silent, silent tomb.
Settling down with his legs folded beneath him, Sakumo lets his eyes fall closed. Solemnly, he places his hands neatly before him and lowers his head until his hair brushes the ground. "Thank you for saving my son," he says softly.
No-one answers. Nothing stirs. The finality of it all presses down from above, thickening the already stifling air.
Sakumo holds the bow until he forgets time, straightening only the ugly, twisting sensation in his chest settles into calm. The darkness still blinds his eyes, but there is nothing more here. No ghost, no lingering, burdened soul.
Obito has moved on peacefully, at least.
A/N: In case you didn't see my tag "Alternate Universe: no Tobi", it means that Obito is actually dead for real. Writing this from Sakumo's POV view was difficult, since Obito's death was always Kakashi's tragedy. Hopefully I managed to do justice to the Kannabi Bridge mission!