To find Kilton, head to the Akkala area southeast of Hyrule and then to the eastern stable in that area. Inside, you will find Moz, who will ask you to take a picture of a strange individual named Kilton. To find it, go to the small left islet of the skull pond which is located to the west of the area. Warning: the NPC only appears during the night. Before questioning him, take a picture of him, then after talking with him, he will tell you that his store is not close but that he is thinking of settling in one of Hyrule's big cities. Return to show the photo to Moz and complete the quest.
Opening of the store in all major cities
To get to the basics, go to the friendly village of Hateno the next night at the place shown in the pictures below. You can of course have fun discovering all its hiding places, but it won't change much. However, keep in mind that his stock changes as you progress and that it may therefore be quite valid to return to see him from time to time.
Functioning, monster objects and utility
Kilton provides a new currency: Mon, collected only from the sale of monster objects (ingredients). With these tokens, you will be able to pick from a stock of very rare items, such as a special ingredient or masks that will allow you to go unnoticed by enemies (moblin mask...). This seller will allow you to acquire a unique set of equipment that we will not reveal here but that should make the fans' hearts beat faster.
Written by Bastien "Lloyd" Dubosq-Luyer. Translated from French by Millenium.us.org.