Anyone who's conquered a Dungeon has met at least the Djinn they are tied to-- if they haven't met others while assisting relatives or companions who have also conquered Dungeons across the world.

But by our strength alone, we're not able to let them manifest at all in this world. Only someone similar to Mister Haru can accomplish that, and there are only four people like that in our world.

...I've met Dantalion once in person, and her strength is added to my own in times when it's needed. Does that make sense Naki? Little Fox?