Katawa Shouju. It's a visual novel about a guy with a heart condition transferring to a school for the disabled. I'm not the biggest fan of the genre, but made an exception for this one.

I should probably plaster a gigantic trigger warning for this one, since, well, the big redeeming quality of this one is the ability to hit a lot of your emotions. I had a lonely childhood and adolescence, and I managed to mostly repress it until Hanako's story arc triggered me pretty badly. If you're particularly empathetic or have a history of loneliness, I wouldn't dive into this one unless you're willing to spend some time processing your emotions and having a good cathartic crying session.