Note: Set in Chapter 485; all dialogue is taken from the manga using my own translation.
"Such an ambition you have...and yet you are willing to change places with this man and die?"
Zoro replies, light-headed with impulse and the loss of blood, "What good is my ambition if I can't even protect my captain? Luffy," he continues, "is the man who will become the Pirate King!"
Kuma says nothing, for which Zoro is grateful. He barely registers Sanji staggering up behind him; is too weary to hear what the cook is saying except dimly, through ears roaring with the sound of blood and his own impending demise. "Give my regards to everyone. Tell them sorry, but they'll have to look for a new cook." What nonsense. Zoro strikes him to stop his babbling, and because the day has been long for Sanji as well and he has been pushed beyond his limits, the blow connects and the cook slumps to the ground. He manages to grab Zoro's shoulder on his way down and flashes an inscrutable expression, something between a grimace and a grin. And then the darkness.
Zoro doesn't stop to puzzle out another one of the cook's cryptic, maddening messages. He doesn't have time. He doesn't care. What does any of it matter compared to the boy lying crumpled amid the rubble? Zoro had hoped, in some small corner of his heart, that this was all just stalling. Even now he half-expects Luffy to open his eyes, smile, and demand a feast, like a crow looking for mischief even after narrowly escaping the hawk. But those eyes stay stubbornly closed, and when Kuma lifts him up with a single hand his body is as limp and unresistant as a rag doll's. Zoro's chest constricts at the sight. It is all he can do to resist the impulse to run forward and snatch his captain's body back from the one who is demanding the payment of a death.
"You're close to death yourself, so it will be impossible for you to survive this," Kuma remarks without emotion, as if it was a detail barely meriting mention. "It can only result in your death." The paw-shaped bubble he pushes out of Luffy's body is as large and wide as a house. It would take up half of the Thousand Sunny's deck. Kuma plucks off a piece the size of Zoro's head and sends it floating towards him, like someone tossing out a bit of mochi at New Year's. "Have a taste and see."
The pain takes him by surprise and he cannot help crying out; even were he not exhausted and injured beyond all reasonable human capacity it would be almost too much to bear. Yet in the moment before he blacks out, he realizes that he has been here before. A long time ago, in another lifetime, he hunted down the circle of someone else's pain. Long ago there was another with long limbs and black hair and large, glittering eyes that focused their gaze on something in the far future; long ago he'd already traded in his life for the sake of a promise.
How large a circle, he wonders, was the agony of a broken neck? How bright the shimmer, how long the afterglow, of a stupid, pointless accident? Did she rest there on the cool flagstones of the cellar floor as his boy-captain does now, with eyes closed and mind already drifting far away, as if in sleep? Or did she lie paralyzed but conscious, the way a broken neck can take you sometimes (as some older boys cruelly told him the day after, right before he shoved their faces into the dirt and held them there until Sensei, his eyes still red and raw, pulled them apart). Did she stare upwards, a scared broken bird, as her breath was cut short and the rectangle of light at the top of the stairs dimmed rapidly, darkening like her eyes, like the future she would never see. What size a circle would such a pain make?
Surely smaller than this. Surely a tumble down the cellar stairs of a small dojo on a small island in the smallest of the Blues could not compare to this pain collected over hours of battle on the Grand Line. What was the sound of a spinal cord quietly snapping compared to the lavish streaks of blood on these stones? What were the eyes of a child who died over half a lifetime ago compared to the unblinking gaze of the future pirate king?
"The location...please let me change it." He heard, maybe from Usopp, that animals often choose a quiet place in which to die. He understands why now; he does not want the others to see right away whatever mangled heap his body is to become. It is better that they never find it at all.
Long ago, he stood and screamed at the entrance to the dojo, hysterical with grief and rage, as if his shouting would wake her up and cause her move the cloth away from her eyes. He looked wildly around for the circle of Kuina's pain, bobbing in the air somewhere just above Sensei's shoulder, found it, captured it along with her sword, and swallowed it down. He did not know what else to do. He did not know how else to keep her.
What had the cook said? "The blossom of death." Yes. The pellet of her pain, no bigger than a seed, bloomed inside him, its vines intermingling with his veins and its roots burrowing deep into his heart. If such a small thing could take him over, what would blood and desperation and the repeated impact of a body on stone do?
Zoro thinks about this as his heartbeat quickens in spite of his resolve. He draws his breath in slowly to steady it; he resists looking back at Sanji's prone figure. He thinks about birds with black feathers and bright eyes. He thinks about the boy whose smile lent purpose to his stumbling steps. He thinks about the existence of heaven.
The shimmering bubble is directly in front of him now. All he has to do is reach out his arms and grab hold, and Luffy's suffering will be his. A death for a life. A promise for an ambition. Zoro does not believe in God, but nevertheless something like a prayer rises up and is released in a puff of breath to be taken skyward on dark, glossy wings. Suddenly Zoro realizes, with a clarity that is far more terrifying than the task he is about to do, that he wants to survive this ordeal. There is someone waiting to hear news of a promise fulfilled. There is someone expecting, when he finally opens his eyes, to have his gaze returned. Just this once, Zoro does not want to have to bargain. Just this once, he wants to find grace.
End Note: 'Kuina' can mean 'rail,' (as in 'Yanbaru Kuina,' the Okinawa Rail) a flightless bird found in Okinawa. Hence the repeated bird imagery for both Kuina and Luffy (who I think of as a crow!)