That's fine - the volume sliders are there for a reason.
Yes, game does give you eight hours, no matter what - Robin's fighting a war here, he can't go around sleep-deprived! Sort yourself out ;) (I'll probably change it eventually to sleep until 6am no matter what, and hand out stat penalties if players get to bed way too late).
I'm glad you enjoyed the encounter between Kana and Maven :) Aftermath events coming in the next update!