Then you're definitely going to want to figure out how you plan to handle combat. It will probably devolve into everyone saying "I kill forty zombie dolphins with my transmuted katana," but at least you'll have tried.
Also, be prepared for the players to go off and do their own thing. Example: I recall an attack on titan rp where the creator expressed frustration that while he was afk, the players had invented a bunch of locations without asking him.
(Always shonen rps. Never any shojo. if someone ever does a Yotsuba&! rp, I call Yanda.)