Isekai (another world reincarnation/transfer) works. Characterized by unique costumes with fantasy elements.
Isekai cosplay is appealing for expressing the 'reincarnated' feeling by combining fantasy elements with school uniforms or modern clothes. The detailed creation of accessories and weapons enhances the world view.
Re:Zero - Starting Life in Another World, That Time I Got Reincarnated as a Slime, and Mushoku Tensei are easy to try with school uniforms + fantasy elements.
Overlord, Cautious Hero, and Frieren: Beyond Journey's End (with magic circle effects) are for advanced cosplayers where decorations, props, and special makeup shine.
