So the guy is living alone or I think in his parents basement/apartment when his sister comes back from the army. She moves back in, but in his space/apartment, that he now has to share. She is in the room on the other side of the wall and he spies on her masturbating. We later find out she put on show for him. She helps him get back in shape. The guy is also overly fond of his rain shower, where you can walk around and the shower kinda follows you.