Rest assured, there is nothing to worry about here – Ys IX: Monstrum Nox has only one ending. If you're wondering about that question, then this is likely not your first Falcom experience.

Does YS 8 have multiple endings?

How many endings are there in Ys VIII? Ys VIII doesn't make this abundantly clear, but there are actually three possible endings. Namely, the bad ending, the normal ending and the best of the lot – the true ending.

Does YS 9 have romance?

Does Ys IX have romance? Ys IX contains relationship events with a whopping 18 characters. They mostly have two requirements each in order to be maximised – complete the request they post (ie, a sidequest) and present them with a specific gift. This will unlock the max affinity bonding event.