Yeah, a little bug called love !
In manga : Oh baby, your sleeping face is so cute.
IRL : Oh... I can't see sh*t.
That depends. When I lived in Japan, my room had no shutters, just a curtain to try to block outside lights and even with that, it was clear enough that I could see around and had to get an eyemask to sleep (can't sleep if there's too much light in a room). Whenever I had some company, I could watch their face pretty much all night if I wanted to without need to have lights on. ^^;