The term futanari is actually a slur for intersex people + it's actually not accurate since people aren't actually born with both parts, so it won't be added into the game due to being unrealistic.
You can add both parts though through editing a save, export save as a file, put it in any save editor, and look for pc body parts, then add "vagina" and "clitoris" at end if you picked a character with penis, or other way around, add "penis" and "balls" if you picked a character with vagina. The save should be at the intro point before you get to customize your character's appearance, then after adding those parts in the edit, you import the edited save and continue on with the game.