They just have a good friendship and understanding, and Nami needs Usopp's tech to hold her own
One Piece
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N
There's only one girl for Luffy and it ain't Nami
>caught up to 3d2y
>I've never felt like such a shipper before.
This is where some of the strongest evidence is. The scene where Nami starts popping off Luffy's flaws uninvited to Haredas is a very common trope in nip fiction where a girl is overly conscious of a guy. There's also: Luffy only seeing Nami's face after he lands on Amazon Lily, and Nami being upset that she can't rush to his side after he does the 3D2Y stunt, although the latter is not nearly as strong as the former two.
Aside from that Oda keeps it very, very subtle. The main scene I always mention that's occured since then is Nami being jealous during the Reiju kissu scene, which is also the strongest piece of intercrew shipbait in the entire manga. We haven't gotten much more major evidence besides that(and the scenes Oda wrote for his movies)
no they don't