I'm stuck like you... a character is sick and i don't know where i have to go...
Do you have find the solution ?
Hello, that is a very tricky part of the game but there is a solution.
You can still carry on with a great deal of the game but if have just hit the point where Summer turns sick then do the below to get her straight back in the party.
Head to the ransacked house (aka World Juice House) to the northeast of フェラヌール. If the flag has triggered then the old man will be there and it will activate the key word to continue the quest. Go north of ルプガーナ and visit the pirate ship. Head down the first stairs where the crew are sitting at tables and talk to the three in the upper right. Head to the captain of the ship and have a chat. You will get an item which you can return to the old man with, he will make the juice cure and then return to Summer with it.
Apologies to the OP, it has been a short space of time since I played and so I'm not sure what the rainbow-coloured doors refer to, if you are still stuck then drop a pic or something and I will gladly help
