This page explains how to recruit Korcha in Chrono Cross: The Radical Dreamers Edition.
Korcha is a young lad from Guldove who makes a living as a boatsman.
How to Recruit
After making the fateful decision to save Kid, Korcha will temporarily join your party when you return to Termina from Guldove. Once you bring the Hydra Humour to Doc and Kid recovers from poison, Korcha will leave your party.
After Korcha takes you back to the Port Town of Termina, head for the town entrance. You’ll discover Glenn and the florist, who are discussing the Acacia Dragoons’ movements since the manor incident. Kid will mention that you’ll need a boat. So return to the Termina docks and speak to Korcha. He’ll lend you his boat and offer to permanently join your party.