It's a seasonal quest shop item, . Each season there are a few items for each of the quest shops that are the highest priced items (like that leaf) and listed last in the shop. For example the winter items for mori and nori are: Tales for Winter Days and Winter Nights, Winter Sky Sticker, and Enchanted Snowman. We give a heads up before a season switch so you can grab any last minute seasonal items, though if you miss out you can always wait until the season comes back around.

That leaf will be back in their shop for Spring! :)