Ken had once heard of how Anglerfish mated, the males were small and pathetic, and when they finally found a mate, they fused with them. For some reason the idea of spending his life fused to a girl's genitals had left an impression on him, and now with this book in front of him he couldn't help but fantasize about how he should do it.
Taking inspiration from his images of succubi in his porn folder, he ended up putting pencil to paper; writing into the human section that their males took on the form of small bat-like creature with a long prehensile tail at birth, which seek out a mate as soon as possible. Once a mate is found, they fuse to their tail bone leaving their wings and tail attached to it, with their male reproductive system being stored inside the female and connecting to her womb so she will be impregnated whenever the male orgasms. Then the male's erogenous tissue, taking on the form of vibrant coloured silk, spreads across the female's skin forming panties fused to her skin, with the male's sight being centred on the area covering her crotch, and at this point their host can hear their thoughts. As the male grows, their erogenous tissue begins to form other items of lingerie covering their host, starting with a bra, then stockings and sleeves, before finally forming jewel like horns poking out of the back of the female's head which allows the male to communicate telepathically with other humans both male and female.
Right before reality began to warp, he quickly wrote down that all humans of both genders can live for over ten thousand years, and are fertile their entire lives. Then everything went black.
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When Ken awoke, he found himself looking at the ceiling unable to so much more than make his silk like flesh shaped like panties twitch and thrash his tail, his wings being pinned under his host's ass. He wasn't sure what colour he was, as it was dark since the sun was still rising.
He was able to find he had something resembling a fly in the bottom of his panty body, being able to pull it open like a pair of lips, to expose his host's vagina. As he let the fly part of his body return to resting position, he noted that the inner layer of the fly could completely cover the vagina on its own, and the outer layer completely overlapped with it. It seemed that this entrance existed to let babies pass through during birth, and yet he was still built to cover her vagina while fused to the outside of it, as opposed to being shifted aside given he couldn't be, or removed, since he's stuck to her.
He suddenly heard his host stirring, it was...