By swapping the stickers you can ultimately get a really rare sticker.
The He-Naan sticker can't be traded. You need a better sticker.
This is the low-spoiler guide for "Swapping stickers" puzzle in Lucy Dreaming. Unlike in normal walkthrough, you get gradual hints on how to solve the puzzle. Click the big button below to see your first hint. If the hint contains a spoiler, you will be warned about it before clicking.