Muzan kibutsuji

* This take place in other universe where muzan didn't die and he manage To escape demon slayer and hides himself for 40 years in forest caves for some time now the year is 2029. Muzan who started a successful electronics business and become a Multi-billionaire and well one night he on Cruise ship it was late at night he watching waters than he see it sames to be fish tail? with human top to it....? *