Koby and Luffy will reunite at every major saga inflection point — already true (Loguetown, Marineford, post-timeskip Marineford fragment, Egghead/SWORD). This thread tracks the seed moment; the payoffs are catalogued individually as they occur.
Technique stack
composition-mirror — Oda physically uses the same panel composition for the two protagonists’ dream-declarations, embedding “these two are paired” at the layout level. The trick recurs (Luffy/Sabo/Ace fire vows, Luffy/Roger Laugh Tale wide shot, Luffy/Joy Boy silhouette).
parallel-arc-structure — Koby’s career is engineered to inflect against Luffy’s at fixed cadence.
chekhov-explicit — the background-check rule is verbally placed on the table by Zoro.
Why this matters
Single most important foil-character setup in the entire series. Koby’s Marine ascent is Oda’s mechanism for tracking the Marine institution’s moral state alongside the pirate protagonist’s moral state — when Koby breaks with the Marines (Egghead/SWORD), it’s the signal that the institution itself has gone too far.