That's probably the result of a cramped space.
Keep in mind, it all takes place inside a some kind of a dorm (although the dev called it apartment complex) affordable by students, so the rooms in such places tend to be quite small.
Yuna has a standard 1-person bed and cuz there's a desk with a chair (just above kaede), there's only so much space between the bed and the door, hence the laying-on-the-floor horizontal position.
Cheers