Using the Kimonos, you can enter to the town of the Old Japan and the warriors will not notice you that you are a foreigner. Also if you wear a complete Kimono, you will notice that there’s something in its pocket, it’s a passport that you will also need to enter the town.
How to Get Kimonos
Exit to the tree house and go all the way to the left until you reach a house before the warriors. Get inside the building and talk to the lady inside the building until she offers you a Kimono. Choose whatever color you’d like, and then go in to your backpack inventory. Select costumize under the Kimono, and put on all of the clothing.