In some 'isekai ojisan light novel', there could be antagonists as well. These could be powerful mages or demons who oppose the ojisan's actions in the isekai world. Their presence adds conflict to the story, forcing the ojisan to use his wits and whatever skills he has to overcome the challenges they pose.
The main character is the ojisan, of course. He is usually an older man who gets transported to another world.
Often, there are other supporting characters in the 'isekai ojisan light novel'. For instance, there might be young adventurers who the ojisan teams up with. These characters are usually amazed by the ojisan's different way of thinking which comes from his real - world experiences. They help the ojisan in his adventures in the isekai world and also learn a lot from him in the process.
I'm not sure who the main characters are exactly as I don't know this work well. But from the title, it seems that a bishoujo and an ojisan would be important characters.
There are characters from different isekai works. Such as Ainz from Overlord, Subaru from Re:Zero, Kazuma from Konosuba.
Since I don't know the details of this particular light novel, it's hard to say. But in most isekai light novels, there's usually a main character who is the one transported to the other world. This character often has some distinct traits that help them survive in the new environment.
Since I don't have first - hand knowledge of the 'isekai no seikishi monogatari light novel', it's hard to say exactly who the main characters are. However, based on the genre, there could be a young male or female protagonist who is the key figure. They may encounter a group of diverse companions, such as a strong - willed warrior, a clever thief - like character, and a gentle healer. These characters would then accompany the protagonist on their adventures in the isekai world.
Since I haven't read 'Tensei Kizoku no Isekai Light Novel', I can't name the main characters specifically. But typically in an isekai light novel like this, there would be the protagonist who is the reincarnated noble. There might also be side characters like a mentor figure who helps the protagonist understand the new world, or rivals who oppose the protagonist's goals in the new world.
In 'Overlord', the main character is Momonga. He was once a normal player but becomes the all - powerful Overlord in the game - turned - real - world. In 'That Time I Got Reincarnated as a Slime', Rimuru Tempest is the protagonist. He starts as a slime but gains many powers and friends along his journey. In 'KonoSuba', Kazuma Satou is the main character, a NEET who is transported to another world and has to deal with all kinds of wacky situations.
There could also be a mentor - like character. In many isekai stories, the protagonist meets someone who helps them understand the new world, its rules, and how to use their new - found abilities. This character might be a powerful wizard or an experienced adventurer in the context of the 'isekai meikyuu no saishinbu light novel'.
I'm not sure exactly as I haven't read it in full detail, but typically in this kind of light novel, the main character would be the reincarnated noble. There might also be side characters like other nobles, servants, and maybe some sort of mentor figure to help the protagonist in their isekai adventure.
I'm not entirely sure as I haven't read every detail of it, but typically in an isekai story like this, there's a protagonist who is the 'cheat magician'. There may also be side characters like friends or allies they meet in the new world, and perhaps antagonists who oppose them.
I'm sorry I don't know the main characters as I haven't read the light novel. You could try looking for summaries or reviews online to find out.