Ahhh, I'm thrilled that you had a good time with it! The bulk of this text was originally written when I was trying to write Lead Into Gold/Serialized Killer as a NaNoWriMo project, and I had these letters scattered between chapters, so that they were filling in the blanks of the main narrative, as the story progressed.
But I'm sure you know how it is when you're writing prose; sometimes the desire to see sprites on screen is just too much! And I found myself really pulled between how I wanted each letter to be read, and which character's perspective I wanted to lean into. The letter-sliding mechanic came from that pure greed to have it both ways. VNs are so wonderful when you're a greedy writer; you get to have multiple tracks and endings and all the intimate character social interactions you want during dialogue. ^U^