I like to think that Cheryl is the game's only actual protagonist, as I also like to think that "Harry" is nothing more than Cheryl's mental avatar. Because, when you get right down to it, the real Harry Mason is dead and is not involved in anything we see going on. In a way, this mental construct serves the purpose of being both a layer of safety and distance behind which Cheryl can revisit her past traumas as an observer rather than rehashing the painful role of acting participant. This also serves the purpose of letting her live out the pitiful fantasy of having her 'father' around, because she seems to think that his absence is one of the primary causes of her life being so shitty.
Remember that "Harry's" personality starts out as a blank slate, and however it turns out, it does so because Cheryl defines it, consciously and otherwise.
This is my sentiment. Until the reveal at the end, you might think Harry is the protagonist, and you might think he is in the chair in the Kaufman sessions.
Harry really does functions as a construct which allows Cheryl to navigate her memories and whatever gaps she is filling in.