Such a cute game!! I was really surprised at just how into the letter-writing I got. You've landed on a really engaging structure! The information gathering phase translated really naturally into the letter-writing stage, and I love that you went through the effort of having all of these different tones and sentences for each part of the letter tailored to that specific relationship. Not only does that effort not go unnoticed, but it really made the whole thing feel alive---there were some letters I tried rewriting multiple times just to see how good I can make it, options that warmed my heart, options that made me wince! In particular, loved the detail about asking the characters how often they talk and if they think their crush loves them back (the one or two that said "No." made my heart race! The drama of it all!)
To really complete the package, I'd love to see some response from the characters after you give the letter (or maybe, more narratively, after they give their letters to their crushes?). It could have a dual role of both giving some satisfying dialogue and also giving some more specific feedback to the player if, after a few attempts, they can't get a higher score on writing the letter. That said, I know that's even extra scripting and writing to make sure that each response feels unique, especially when the rest of the writing is as detailed as it is. I think even without it right now, the characters have a lot of life and charm to them.
Great work!! Thank you for sharing! :D