Once the surprise of the fluctuating bar charts to the left side of the screen wears off, the game is quite simple: Stimulate a part while keeping an eye on one of the four top bars. Continue only as long as it is going down. Once it started going back up, stop. Then either resume stimulating or go to another part. Once you've done enough, the game enables a "next attack" button, allowing you to proceed to another scene. There are four scenes in total, haphazardly arranged. You see all of them in the screenshots.
In case of eye candy and enjoyment, the game offers none. It is censored. Even without the censorship, you have to keep your eyes elsewhere. The good drawing quality and excellent voice acting is wasted.
The backstory is more interesting. It is extremely implausible. It has five major logical loopholes. Try to find all five. I assure you, your time is better spent doing that than playing the game itself.