The voice with which the letter is written is very charming, I love the idea of our choices determining the relationship that we have with this anonymous writer. I'd appreciate even more interaction with them in the coming prototypes like dictating if the relationship is romantic or platonic.

I think with some more versatile images and aesthetics this game could bypass the boredom that may come with a very static game play loop

As another has noted, it wasn't clear that the character being controlled is reading a letter. On my third playthrough - there are plenty of clues about that, more observant people will notice, but I think these are sort of details that a lot of players will skim through while looking for parts of text that are most important for the main story. A different, more handwritey font for letter contents would probably help.

Other than that, looks like a great atmosphere, and that cook's life is intriguing, very good main character material.

The loop is compelling, and from what I gathered you're able to define your character in an engaging way that subverted my expectations at first. I just got a bit lost later on in the shuffle between who the protagonist is and who I am. While the epistolary style works really well (and makes for a great interface to go with the board concept), it's not entirely clear at first that the player's responses are their thoughts, so it may need some more framing/setup. 

Would also be an interesting sci-fi concept to combine the letter and diorama into some kind of futuristic document that reacts to the user's subjectivity/thoughts, which could lend some tragedy in how the account you're being given is highly subjective, highly excessive and user-optimized to the point of being counter-intuitive.