Worker's Lament (Side Quest)
This quest is available in Letopolis.
Follow your marker to a pregnant woman moving grain in Letopolis.
Speak with her for an objective to check up on her workers. Senu will help you locate them in a dry well.
Drop down inside to see that there's been a tunnel collapse, and two men are still trapped.
Smash open the wooden door to find the first man.
Carry him out and leave him in his brother's care, then return to the passage. You'll have to smash another wall, then kill some snakes in a cavern leading to a ruin. A spear works well for the job.
Once inside, speak to the third man. He's fine.
He'll go on his own way. If you don't want to retrace your steps, you can use a fire arrow on the flimsy roofing at the far end of the revealed library.
Note that you can also pickup 'The Old Library Quest' here.
Exit the ruin, and return to Nito for mission completion.