I just played through half of the entirety of a game called "Futanari Kanon-chan" that came out a few days ago. It's not everyday so to speak that you see a game that centers around the concept of a dickgirl, so I gave it a try. There's another futanari game coming out in January as well.
This game is low budget and comes from one of those minor status, ero-oriented companies and you can see it. The interface is very simple with little eye candy. I thought it would be simplistic in story and characters too but I was pleasantly surprised by how decent the plot is and how well-executed the main character. Every character is voiced except for the males, and the main character is fully voiced as well, her dialogue, h-scenes, and monologues.
The game's main character is Shinonome Kanon, who was an ordinary girl until one day she woke up with a penis between her legs for some yet-unexplained reason, making her into a futanari. She keeps this development a secret from everyone else, fearing that they'll hate her and that she'll get expelled from her all-girls school and be shunned by society in general. Thus she has tried to continue her normal life to the best as she could while grappling with the issues and depression her condition causes her.
She's fairly hot and cute, lacking in self-confidence, and very nice to everyone...... unless she happens to be turned on and you happen to be a cute girl standing next to her, in which case RUN. RUN for your purity and maidenhood, because Kanon's sex drive is
UNSTOPPABLE.
(it's much like this eyecatch implies)
It's not that she likes it or wants to be that way, but once her thing gets big (and it gets big frequently I tell you) it's gotta be taken care of somehow, preferably by herself, which she does frequently thoughout the game, but if a cute girl happens to be there and accidentally rubs Kanon's thing the wrong way..... well, young lady, we'll pray for your safe passage into the land of sin.
Her voice is high-pitched and I didn't feel comfortable with it at first but then grew to like it. Especially during the h-scenes.
The other characters are Matoba, who's Kanon's energetic kouhai who tries to support her sempai whenever and however she can. Yuki is the prim and proper student council president, while Kanon is the vice-president. Maya is the newly-appointed health teacher. There are also minor characters like that hideous bastard of a PE teacher, who's the closest thing to a villain in this game, who's a sadist who also likes to molest the students.
Kanon's a great character. Her lack of self-confidence, her struggle with her condition and her wish to become self-confident again and regain her normal, happy life, all make her a good character, but she becomes great in my opinion because she's not just nice, and self-pitying all the time. She can succumb to the stress or get mad at people too, so to speak. She doesn't just stand there and take it like some one-dimensional character.
Did I mention that she has a massive sex drive? Yes there's that, and the fact that this game is still one of those small, ero-oriented game. The game's opening scene is of her furiously beating it off in her bed in the morning because if she didn't she'd never get her morning wood into her underwear. But seriously, her sex drive is really something. And this game is raunchy, like Prima Stella raunchy, without sound effects, and with mainly girls. This game isn't that short though. I guess it's about a little less than normal ero-game length. Oh and lastly the music is actually pretty decent.
This game, in my opinion, exemplifies everything about the futanari fetish that makes it so appealing to its fans, so if you want to know why people like the fetish, this game would be an excellent way to know.
Enjoy, and watch your behinds!
EDIT: Actually I was mistakened; this game is pretty short. The whole thing is probably the length of a typical eroge's route plus a little more.