Ch. 45 plants four recruitment-conditions in a single chapter:
Luffy issues the recruitment offer (pages 5-6, “You’re a good cook, and you’re joining my crew!!”)
Sanji’s reason-to-stay is set up as withheld (page 5, “I’ve got a good reason for staying here.” — see Sanji Stays For A Reason)
Nami’s presence is added as a recruitment vector (page 18 — Sanji’s love-at-first-sight; “I would stoop to becoming a pirate, or even kill, if only I could be with you ♡!”)
Zeff’s permission-to-leave is granted (page 18, “I don’t need you here anymore. Follow your heart. Go be a pirate.”)
A fifth, the external-pressure trigger, is set up in the chapter’s final pages (Krieg’s inbound arrival).
Why this matters
Every Straw Hat recruitment requires a prior-allegiance-dissolution beat — the recruit must be released from a prior bond before joining. The release can be:
Master-granted (Sanji here, Chopper later via Hiriluk’s death)
Self-disbanded (Usopp’s Ch. 40 disbandment)
Forced (Robin’s Crocodile-betrayal)
Handed-off (Jinbei from Sun Pirates)
Ch. 45 sets up Sanji’s release as master-granted — the cleanest archetype. The four-condition setup is unusually front-loaded for the recruitment-pattern: Oda compresses four recruitment-conditions into a single chapter, signaling that the Baratie arc’s recruitment-resolution will be more emotionally intricate than prior recruits.