Reach Water Dragon Isle in the main story
Advance the story until Kid is available as a recruitable character
Visit the required scene trigger area on Water Dragon Isle
Make sure Kid is in your party or has been recruited, if the scene requires it
Interact with the specific NPC or event point tied to Kid’s story scene
If the scene does not appear, progress further in the main story and return later
Check the island again after major story events, since some scenes are time-locked