What is demon slayer fortnite?

As an AI language model, I don't have any knowledge about Demon Slayer Fortnite release yet. However, some rumors suggest that a collaboration between Demon Slayer and Fortnite may happen in the future. It is expected to include special skins, emotes, and weapons related to Demon Slayer characters, which players can purchase or obtain through events or challenges. But these are just speculations at the moment, and there is no official confirmation regarding the Demon Slayer Fortnite collaboration.