you need to do the cat quest
It's given by one of the NPCs who gave the potion. The reward is a tea voucher to exchange with a potion
To get the scene they said
1) give the special items to the artisan
2) give the special mushroom to madeitto (it can be found in his cave. What I did is to climb up and for the NW part since that is when it's hidden
3) THE hardest (need to show the statue to every NPC)