Often, the monster itself is the protagonist. It goes through the process of reincarnation and all the adventures and challenges that come with it.
There can also be a hybrid protagonist. Maybe a half - human, half - monster being who has a special connection to the reincarnation process. This character could be on a quest to understand its own existence and the nature of reincarnation, all while dealing with the unique challenges that come from being part - monster and part - human in a world full of pure monsters and humans.
Often, it's the curious ones. People who venture into unknown areas without fully understanding the risks. Like explorers in a jungle where a giant snake monster lives.
Often, it's an ordinary person. Maybe a scientist who experiments on themselves and accidentally turns into a monster. Or it could be a young, curious individual who stumbles upon something that causes the transformation.
The protagonists often include a human male who is curious and open - minded. He might be a young adventurer or a scholar who is intrigued by the unknown, which leads him to encounter the monster girl. The monster girl protagonist can range from a shy and gentle lamia to a fierce and independent kitsune. Their differences in nature and background create interesting dynamics in the story. They both have to overcome their own insecurities and the challenges that come with their relationship.
Often, the protagonist is a young girl or woman. She might be an ordinary person with no special abilities at first. For example, she could be a schoolgirl just going about her normal life until the transformation occurs.
Often, it's a regular human being. Maybe a fisherman who has a strange encounter at sea and then starts to transform. Or a sailor who's been cursed.
The typical protagonists are often the slaves themselves. They could be ordinary humans who have been captured by the monsters and are now in a state of bondage. For example, in some stories, a young peasant might be kidnapped by a group of troll - like monsters and become their slave.
There's the monster, of course. It could be a big, hulking creature like a werewolf or a more mysterious one like a vampire. Then there are the humans who misunderstand it. There might be a hero figure who eventually realizes the truth about the monster, like a brave knight or a clever detective. And there are often bystanders, ordinary people who are afraid of the monster without really knowing it.
The monster usually plays the role of the antagonist, causing fear and chaos for the main characters.
There may be a partner of the impregnated person. This character could be in denial, or trying to support in a difficult situation. Another character could be a mysterious figure, like a witch or a seer who has some premonition or knowledge about the monster baby. And there are usually bystanders or other members of the community who react to the impregnated person in different ways, either with fear, disgust or pity.
It could be that the story doesn't follow the traditional rules of reincarnation. In a typical story, there are often karmic consequences or a purpose to the reincarnation. But in this not - so - typical one, there might be no such clear - cut reasons. The protagonist might be constantly confused about why they are reincarnated and what they are supposed to do, and the story could explore that confusion in a very different way from other reincarnation tales.