If Toan visits Claude in the morning, he'll give him the "Candy" lollipop.
This is missable if Toan doesn't visit him in the morning. Claude will be asleep during the day, and will give him Cheese (instead of Candy) at night.
If the Candy lollipop was not received from Claude in Norune Village, then it can be obtained from Couscous in Matataki Village. If Toan refuses the offer, then he'll hand over a Fire or Ice weapon attachment, and if that is refused, he'll hand over the Turtle Shell.
If the Candy lollipop is missed from Couscous too, the trade quest will end and the Sun Gemstone will become unattainable.
The "Ointment Leaf" can only be obtained in exchange for the Candy lollipop. This will happen during Bunbuku's House Georama event. Bunbuku will ask Toan if he happens to have a Candy lollipop, because he mistakenly ate the one that Kululu had. In return he'll give up the Ointment Leaf, which can be made into a cure-all medicine (akin to Lao Chao's Miracle Dish, in Dark Cloud 2).