The set is sold by one person: the ugly Kilton, a salesman specializing in monster products. The first step to own the set will be to unlock the store of this atypical character.
After that, it is only a question of patience and tenacity. As you progress through the game, go back to him at regular intervals, he will often have new items to offer you, the last ones being the famous black clothes that everyone wants. Please note that you will still need to pay more than 3997 Mon for the complete set! As a reminder, the latter are obtained by selling monster materials only.
Written by Bastien "Lloyd" Dubosq-Luyer. Translated from French by Millenium.us.org.