New players usually miss out on EX chapters cause they think they are just side stories and hence miss out on a lot of context. So I suggest adding a menu option with list of all the chapters in chronological order, including some event stories like Christmas events, Elegy of nightmare and even Golden Vortex.
There should also be a warning message of sort to tell the players that which chapter they haven't played, but still not outright locking them out of trying the new story chapters.
#Story chapters order/precedence list
pseudo sail