Roronoa Zoro stands alongside Monkey D. Luffy and Nami as a central figure. The story opens with the trio desperately adrift, weakened by starvation, before a plesiosaur destroys their dinghy, separates them, and washes Luffy and Zoro onto a strange shore. Demonstrating significant resilience, Zoro quickly regains consciousness and leaps into action against the pirates enslaving the island. Inside the Devil's Tower, his formidable swordsmanship enables him to fend off multiple crew members, protecting the local girl Medaka and supporting Luffy. His loyalty drives him to cooperate with Luffy in freeing the island, even following him into the tower despite risks and showing exasperation at Luffy's impulsiveness. A recurring trait, his poor sense of direction, is subtly hinted through context.

Zoro fights in the climactic clash against Ganzack and his forces. He is captured and shackled after surrendering to prevent harm to enslaved villagers, revealing pragmatic concern for innocents. Later freed by the secretly rebellious Nami, he reignites the fight. He confronts pirates on the deck of Ganzack's transforming Devil's Tower warship and prepares to battle the returning plesiosaur before villagers intervene with a fireship. Following Ganzack's defeat, Zoro leaves the island with Luffy and Nami aboard a new boat given by grateful villagers, supplied with food and carrying Medaka's life preserver gift, sailing onward as part of the crew.