Unfortunately I'm not sure I understood exactly what to do in regards to going to sleep. I kept killing the monsters and then realizing my time had run out (would be nice if there was a sound effect when it was close to ending). When swapping to the other characters I could sleep sometimes and even once put the "main" character to sleep as another character, but I wasn't able to get them to sleep all at the same time :/
The game is intriguing enough that I tried a few times and want to know more!