Zeliard is one of those rare example of a Japanese PC game (the PC-88, one of those Japanese home computers who were rather unknown in the West then) getting a translation and official release overseas.
It’s an early example of a 2d-action RPG, as you get experience points for killing enemies and once-upon a while you level up, though its nothing you have any control over. You don’t have any skill points to invest, it’s merely HP/MP/damage upgrades (which is rather typical for how 2d-action RPGs handle this).
Your start in a city, the capital of the kingdom where a demon just petrified the princess, and are tasked with finding a cure and a way to stop said demon. Enter successive dungeons of ever-increasing complexity to find him, though this is easier said than done. These are no small levels, these are large, expansive, free-roaming dungeons connected with each other by small cities, and you can traverse the whole combined world at will.
The levels in Zeliard have a strange topology. Start at an arbitrary point and go right, and you will reach the same point again (the same goes if you go left, up or down). This makes mapping the levels rather complicated, but without maps you will be completely lost, especially in later levels.
I’m not sure if Zeliard is the first example of a 2d-action RPG, but it’s definitely one of the most memorable early once that successful merged 2d platforming and RPG-aspects, and it’s not just the obvious stuff like experience points and level-ups, but also the whole dungeon crawling experience, the cities as a place to rest and gather information and buy stuff, it’s pretty much what you’d expect from an RPG.