Ah, I didn't make it obvious so that's on me. The darkness doesn't help either...
Just above where you enter the second area, there's a shade (it's the same one, but you can't really tell because they look the same XD)
Talk to him a couple times, and then you get access to the sleep mechanic. Convoluted, I know. Sorry ;-;
Note: When you can't sleep anymore, just go back to talk to him again.