Beyond Reach is a letter-writing game about unrequited love for (and from) a giant robot.
It's very niche, but also very good.
Weirdly, there is a lot of communication, but it's very restricted. You only see part of what your counterpart is doing or thinking, and it's generally just the surface of it. This is a super effective device, and it makes the reveal at the end when you (maybe) get to see each other's letters hit harder.
The game text doesn't push too hard into the tragedy (you, as the players, supply that, as much or as little as you'd like,) and there's a neat gameplay chart at the back of the book that explains the rules extremely clearly if you get stuck anywhere.
If you enjoy letter-writing games and you don't mind a bit of sadness, I would highly recommend giving this a try.