An addition to one of my past suggestions, specifically about fly larvae.
After they return back to the uterus, after hatching, they need something to eat. And for this, sperm is perfect, which, as I understand, also has 3 stages of filling. Ok, 4. Missing, few, medium and many. However, at the same time there is no ceiling on the litre, which is strange. It is necessary to introduce a limit to one liter or two, because now there is no one and the character can safely carry at least 15 liters.
Although this is also a lot, and I'm not sure that in reality the uterus could accommodate so much, but this is a hentai game so fuck it. And when the amount of sperm exceeds this ceiling, the character reproduces a special animation in which the cervix spontaneously opens, and a certain amount of sperm flows out. And the stage ... fill - ins ... I do not know how to know it, it decreases by 1.
For some reason, I am sure that if something like this happened in reality, it would be at least painful. Girls, confirm or deny. Therefore, a certain amount of health should be taken away from the character. Or it shouldn't, I don't know.
One larva eats 100 ml for development, respectively, the amount of sperm decreases in proportion to the number of larvae.
The smaller the sperm, the slower the development of the larvae and, therefore, they will stay inside for longer.
As I said before, after the larvae develop into flies, they begin to attack the heroine in order to fertilize her again.