The first time, it should be illegal, it feels illegal to Zoro at least. He's fucking an 18 year old and at 24 he's never felt very old. Right now he feels like the dirtiest old man for miles around. He's fucking a barely legal teenager right next to an actual child, which is unfair to Luffy as he's 17 and their captain. And fuck he needs to stop thinking about the pile of toned muscle and warm skin in the boat next to him and how his dick is getting harder if that's even possible while he's pumping in and out of the witch's sinful cunt. But he can see her looking same as him, and if she's not going to say anything about how they only fuck each other when they could reach out and pull Luffy into their boat and in-between their bodies. The navigator and the swordsman are in love with the captain and they're both too chicken shit to tell him. And Nami is coming, clenching around him like a vice, and she bites into his shoulder as she moans Luffy's name. Zoro's only half ashamed he follows her, hips faltering in their rhythm and he grunts the same name she buried in his skin moments before.
They lie together basking in shares what-ifs before pulling apart. Zoro tucking his cock back into his pants and Nami moves her panties back in place and pulling her shirt over her tits. Zoro leans against the side of the smaller boat and watches as Nami slips across the gap that separated their quick and dirty fuck from the captain's sleeping form. Nami slips back into the place next to the captain that's always open for one of them to fill. The anchors are dropped and they won't need her to navigate them to the next island until dawn so she allows herself to settle in beside Luffy and let him pull her closer to him like she was a stuffed animal before drifting off to sleep.
Before Nami took the Going Merry back to hell on earth, to the man that owned her, Usopp was the only member of the crew that slept in the hammocks. Zoro slept on deck which was no surprise to Luffy and Nami who were better acquainted with the swordsman quirks. Nami insisted on taking the only bed as her own claiming that not even savages would force a women to sleep in the same quarters as men. Luffy would sneak into Nami's bed curling around her and they would wait until it was Usopp's watch and Zoro would silently creep into Nami's room and watch as the captain wrapped himself around the navigator as she fingered herself in front of the first mate.
After they pick up Sanji from the Baratie and Arlong Park is in ruins Zoro comes into her room and strips off his bloodied shirt and discards his swords. Slipping into her bed and sandwiching her between Luffy and his chests. She's surrounded by the scent of sea water and blood, something that she has been haunted by for years but now it lulls her into a peaceful sleep.
In loguetown Nami laughs as Zoro gets lost between her thighs and after she comes all over his face she stuffs her hand down his pants and Zoro comes to the sound of Nami's voice as she whispers fantasies of someone else hand joining hers so caught up in the moment that it isn't until he escapes the Marines and the women with Kuina's face and dreams that he realizes that Nami slipped the 20,000 beli into his back pocket as she got him off. He doesn't end up using the money, but she refuses to take it back and publicly declares her claim on him in the form of an ever growing debt.
—
As Nami learns the weather and currents of the Grand Line during the trip between Whiskey Peak and Little Garden, she spends nights sandwiched in between Zoro's thighs Nami's quilt wrapped around them. Her eyes flicker between the horizon and the Log Pose on her wrist; Zoro keeps watch on Luffy who falls asleep on the newly repaired figure head. Now that Nami shares the Captain's quarters with Vivi the trio tend to sleep on the deck despite the weather, keeping watch on one another.
In the baths, Zoro gets to see Nami give her audience an eyeful, which seems to grow the farther away from Cocoyashi and Arlong. The more she loses the starved look in her eyes and her fear goes with it. The pervert in the kitchen knows how to get her to eat even when the food in the fridge is dwindling because of their captains appetite. The whole crew takes up fishing in an effort to keep everyone's bellies full. She sits out on deck now with Robin at her side making maps of where they've been