These are exactly the games that inspired the feeding mini-game in my game Feed My Affection - A Weight Gain Themed Dating Simulator, as @Aeremis mentioned.
If you’re interested in using Ren’Py for this, you can download my game and take a look at the script file “feeding.rpy” to see how I did it. I am likely to rewrite most of it now that I am working on a new inventory system though.