Japanese pop culture - mangas, animation - enjoys recognized success in France. Trading in these objects implies catering for the particular public of fans who tend to consider themselves as experts. Professionals therefore sometimes have difficulty asserting their competencies, and this complicated cohabitation can lead to conflict. The ethnographic study of a shop in the city of Lille shows how salespersons have tried to establish their own categories in order to mark the limit between their professional status and the community of fans.