Katawa Shoujo is a "visual novel" — a story told through a game with text, pictures and music. A typical visual novel allows the player a limited amount of control over the protagonist's story, in the form of choices. Because many such games involve "routes" that establish romantic relationships between a male protagonist and various female characters, they are often called dating sims. Like many VNs, Katawa Shoujo includes erotic content, but this can be disabled in the options.
The game is free to download and will install on Windows, Mac OS X, or Linux. There is an "Act 1" demo if you just want to try out a bit, though the best material requires a full playthrough.
The game's protagonist character Hisao is sent to a special school after being diagnosed with a congenital heart defect. His new school caters to people with disabilities or physical problems, and he meets several girls with their own unique conditions: blindness, deafness, missing limbs, burn scars, and so forth. Each of the characters he meets has psychological complications of their own, some tied to their physical condition, many unrelated.
Through interactions with the girls, Hisao — and the player — will learn more about them, and about the nature of "disability", the weakness of the human heart, and the strength of the human spirit.
The game is an amazing storytelling experience, turning what could have been a pandering eroge concept into a sweet-natured and insightful look into a handful of peoples' lives. Each of the girls has her own unique nature, not all of them get along, and none of them are looking to be taken care of. The player's choices, knowing when to help and when to back off and let a girl stand on her own, are sensible and understandable.
The art, music, and other production values are good. The game is a good showcase of the Ren'py VN engine.
The game can be offputting if you don't give it a chance, because its central concept could be seen as exploitative. As usual for the genre, several replays, taking different routes, are needed to extract the whole of the story, and there are a few inconsistent details in timing, geography, and motivation that emerge if you're looking for a sense of the whole thing.
If you are someone who doesn't mind guiding a male protagonist through a relationship with a girl, and want to see a really well written example of the genre, you should play this game. If you dismiss such games as "fap material", try this one — it might change your mind.