Usopp’s captain identity is the wound he carries into the crew when he
eventually does join — payoff in the Water 7 / Enies Lobby arc when Usopp
splits from the crew, becomes Sogeking (his own captain again, masked), and
has to be reconciled before rejoining.
The Usopp Pirates swear loyalty to a captain who tells obvious lies — the
seed for the crew-as-believers-in-the-captain’s-dream framework that the
Straw Hats themselves embody (Luffy’s “Pirate King” claim is the same kind
of obvious-lie-the-crew-believes).
The recruitment beat where the recruit pitches captaincy and is refused is
a new sub-pattern in Oda’s recruitment grammar (recurs with Brook’s
century-of-solitude self-importance, Jinbei’s age-and-bounty seniority).
The payoff
Earliest known caller
Ch 23 pages 8-9 — the Usopp Pirates title-cards are the seed; the payoff lands 350+ chapters later.
Why this matters
pre-recruit-captain-status — Usopp is the first Straw Hat recruit who arrives with a captaincy already in hand. Zoro/Nami were recruited solo; Usopp is recruited out from under his own crew.
anti-recruit-grammar — the recruit pitches captaincy and is refused sub-pattern starts here (recurs with Brook, Jinbei).
wound-as-recruitment-seed — the captaincy self-conception is the wound the Water 7 arc cuts open. The seed is planted at recruitment, the wound surfaces 300+ chapters later.
long-burn-payoff — the single longest character-arc payoff in the series for a seed planted in the recruitment beat itself.