It's interesting that it 'feels' like a horror game with the creepy house, rain/thunder, and flickering lights, but it never actually goes there. Like Sam and Lonnie looking for, but not finding any ghosts, there really isn't anything else there other than your imagination. Entering new areas like the basement or the attic, you expect there to be some big fantasy mystery revealed, but it's just more details on a more grounded love story. The little elements like the hidden passages, Ouji board, and the 'exorcism' add to that fantasy, but it's just the developers getting the players to internalize that feeling.
Also, there's one letter that describes the first time the two girls actually have sex, but the player is prevented from reading it for more than a few seconds. If you Google the note, there really isn't anything there to write home about, but I thought it was a really interesting move for Katie to assert herself on the player. The entire game is the player rummaging around this house, reading notes and letters, but in that one moment, Katie stop you.