The mc ends up falling down into the deepest part of a dungeon. There he is saved and healed by some sort of spirit who takes a liking to him. Another spirit who acts like a mother to the other one then trains the mc so he's strong enough to leave the dungeon. When he leaves the spirit who trained him tells him to take the other with him and protect her so that she can see the world. The spirit who trains him is stuck in that location and can't leave, and mc is also tasked by that spirit to find her siblings and talk to them.