The best I can figure is that it's supposed to be three different uses of the "haa" sound.
The first when she's stretching her neck after reading.
The second I'm guessing that she must have had her nipple rub against her leg when she leaned over (hence the blush) and let out a "haa!" in...
Based on where the entrance is, their apartment seems to have no bedroom, it’s just a one room (with bathroom). The sofa looks like it can convert into a bed, so I guess they sleep together on that?
It makes sense when you think about it as being a content warning for people that really want to avoid reading that. When I realized that, I understood why it is the way it is.
Though a better solution would be the ability to tag specific chapters with that one and the Gore tag for series that...
I need to catch up on this at some point but the place I was at was among the chapters that got wiped out so I’ll have to look elsewhere at some point.