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Summary Sometimes people can forget he's sitting there sleeping. That's why Zoro knows all. L/N Post-Arlong.
Zoro always sleeps above deck. Rain or clear skies, he always is curled up in some corner somewhere, usually ready for an emergency. It was a habit from when the ship was very tiny and sometimes the captain would rocket over the edge by accident in his sleep. He knows that sometimes Luffy wanders the deck at night and he always has one ear open in case he has to rescue his captain.
Hearing footsteps on the deck, his senses recognize them as Nami. He's slept out here enough during the day that he knows who is crossing the deck without fully having to wake or even open his eyes. He shifts his position subconsciously in his sleep so she can't see him. He doesn't feel like talking and doubts she does too.
After a while, he falls deeper in sleep before he can hear the familiar noise of his captain approaching. His ear pricks slightly, waiting for a sound of splashing. Someone's leaning on the railing now. Zoro knows that he needs to definitely keep paying attention incase Luffy goes overboard. It's true that Nami is strong enough to save Zoro from drowning, but most don't realize that even though Luffy is rubbery and looks like he would wear almost nothing, he is actually very heavy, certainly too heavy for Nami.
"What are you doing up?"
Zoro keeps himself from jumping. It's only natural that they would figure out he wasn't sleeping completely. The three of them have been crewmates for several months now.
"I could ask you the same thing."
Zoro knows that they either don't know he is there or they think he's sleeping soundly. That works for the swordsman. He doesn't want to be bothered with moving.
"Look," Nami speaks, her head clearly turned away from Zoro. He isn't listening, but if he wants to stay alert enough, he can't tune them completely out either. "Just…" Nami pauses as though searching for what she wants to say. "Thank you."
The pair fall into silence and the swordsman finds his ears turning towards them wearily. One time, before Sanji joined the crew, Luffy and Nami had been talking late at night and after a very long silence, Luffy had accidentally fallen in. Even though Luffy hadn't fallen overboard in a very long time, Zoro still waited, remembering all the times even before Nami joined them.
"You're wel - " There's shuffling on the deck and an odd noise. One of Zoro's eyes open to make sure everything is alright and he quickly shuts it again. Nami has her head bent so her eyes are buried in Luffy's shoulder, her hands clutching the fabric of his vest. She looks like she might cry again, but no sound comes out. It was a very personal scene, one that Zoro knew he shouldn't have witnessed.
Silence reigns for the longest time and then there's shuffling on the deck again, most likely Nami let go of Luffy. By the slight creak he hears, Zoro knows that someone is leaning on the railing now and he can hear Luffy shifting his feet.
"Sorry," Nami murmurs.
"It's okay," Luffy replies.
Again there is silence as Zoro waits. He knows that most likely everything is under control, but still he pays attention just in case he is needed.
"Can I ask you something?" Nami's voice comes after a time.
"Why - " she cuts herself off and then pauses before saying, "Never mind."
"What were you going to say?" Luffy presses slightly.
"Nothing," Nami replies after a bit. Then she takes a few steps away. "I'm going to go to sleep now." After a few moments, she takes another step before her feet go back the way they came. After she stops walking, there's a slight silence and then she begins walking again before heading down the steps to her bunk.
Again the night is silent. Zoro remains still, feigning sleep, more alert than before now that it's only Luffy on the deck. Finally he hears the sound of Luffy's sandals walking away and off towards his bunk. Certain that no one is around, Zoro stretches his legs out and opens his eyes, still invisible in the night.
If there's a demand for it, I might do this from Luffy and Nami's side of things, but for now, this should suffice.