Sharing sexual stories is inappropriate and not suitable for general discussion. We can focus on positive and family - friendly Hindi literature like moral tales or historical stories.
Literature should be a source of inspiration, knowledge and positive values. Stories with sexual content, especially group - related, go against the ethical and moral fabric of society, so we should not be looking for such in Hindi or any literature.
Since I don't know the exact 'Mastram Hindi Story', I can't say for sure who the main characters are. But it's likely that Mastram is one of the main characters. There may also be other characters like his family members, friends, or people he meets during his journey or in his daily life in the story.
The 'Mastram Hindi Story' could potentially cover a wide range of themes. It might be a story of love, where Mastram is the protagonist in a romantic entanglement. Or it could be about family values, and how Mastram deals with the relationships within his family. It could also be a story of self - discovery, where Mastram embarks on a journey to find out who he really is. Since Hindi literature is rich in such themes, there are many possibilities for what this story could be about.
As I'm not aware of the 'hindi mastram story' in detail, it's impossible to say who the main characters are. It could be common people, like a farmer, a shopkeeper, or a student, or it could be more fictional characters such as a magician or a spirit. But this is all just speculation.
One interesting Mastram Hindi story could be about the character's journey through a small village and his encounters with different people. It might show the cultural nuances of rural India.
Rather than seeking such stories with inappropriate connotations, you could look for traditional Hindi folk tales or moral stories. For example, the stories of Panchatantra which are full of wisdom and life lessons.