Of all Tengai Seibo stuff, this is my favorite set. Unfortunately, I can't find the actual text set anymore (just image set). I know it was some sort of web image novel, with "next" button for the next part of the story, with one pic in each page. The story was not bad either.
Makoto went to a mountain for some reason (I think her father died or something) and found that insect. She decided to raise it. One day, it was having an erection, so she decided to "satisfy" it as its carer. Then things went from one end to another, and she liked having sex with it. In summer vacation, she decided to just move in to the cave and had non-stop sex for several weeks. During the time, she saw that it was evolving and will probably fly away, so she decided to bear its child. After impregnating her, it cocooned itself. 9 months passed, and she gave birth. At the same time, it hatched and flew away. The end.
I don't remember reading the 2nd part, but it's pretty obvious from the pictures.
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