Green Zone is a large island containing the NPCS Marine Lieutenant, Marine Captain, and Fajita. There are miscellaneous NPCs, which are The Alchemist and the Mysterious Man. You can get a mythical sword style called "True Triple Katana". If you have all 3 legendary swords Wando, Saddi, and Shisui with each sword having 300 mastery or more it could be bought for 2,000,000 Beli at the top of the highest stem in Green Zone, from the Mysterious Man. The Green Zone is also a spawn point for the Legendary Sword Dealer which spawns in a leaf and near fajita and Master Of Enhancement by the docks. The quest giver gives you the quest for the three NPCS listed above. The NPC that will take you to the Third Sea is located beside the boat sellers beside the bridge.
The theme of the Green Zone is The Living Forest, which was composed by Roblox.