Yosaku (page 7, panel 4 → page 8, panel 4 of Ch. 69): “In exchange for becoming one of the Seven Warlords, Jimbei released… a holy terror into the East Blue.” / “Arlong’s a fish-man. He used to be Jimbei’s equal.”
Two coupled seeds:
Jinbei is named for the first time — leader of the Fish-Man Pirates, one of the Seven Warlords. First on-page reference to a character who eventually joins the Straw Hats (Ch. 1058). The Ch. 69 install is the seed of the longest-deferred Straw Hat recruitment in the series — ~989 chapters to payoff.
The Warlord-license-with-consequence doctrine — the WG is willing to trade worse-evils-for-lesser-evils to pacify high-tier threats. Forward-payoff: every later Warlord arc (Crocodile/Alabasta, Doflamingo/Dressrosa, Moria/Thriller Bark, Blackbeard/Marineford, Hancock/Amazon Lily) operates under this morally-compromised pacification logic.
The Arlong-arc’s emotional weight derives from this single doctrine: the East Blue’s peace is a fiction maintained by Jinbei’s morally-compromised Warlord-trade.