Selling it as a peripheral, without authorization, but it says: Is cosplay considered an copyright violation?

Unauthorized use of the copyright owner's characters, storyline, or other intellectual property rights may constitute an copyright violation. Although they could sell merchandise in the name of cosplay, if these merchandise actually imitated the copyright owner's work without their authorization, it might constitute an copyright violation. Therefore, in order to avoid copyright violation, it is recommended to obtain the authorization of the copyright owner or use the authorized sample or substitute when selling the surrounding products. If they did not obtain authorization, they might face legal proceedings or other punishments.