Power progression is a common theme. The main character often starts weak in the new world but gradually becomes very powerful. For example, in 'That Time I Got Reincarnated as a Slime', the slime character gains various abilities and becomes a strong leader.
Another theme is exploration. The characters explore the new isekai world, discover new races, cultures, and magic systems. In 'Overlord', the main character explores the game - like world he is now in charge of. Also, harem themes are quite common where the main character is surrounded by multiple characters of the opposite sex, like in 'Konosuba' where the main character has a group of female companions.
One common theme is self - discovery. The female protagonists often find themselves in a new world (isekai) and through their interactions with different characters, especially potential love interests (otome aspect), they learn more about themselves. Another theme is romance, of course. There are usually multiple male characters that the female lead can develop feelings for. And the theme of adapting to a new environment is also prevalent. Since they are in an isekai world, they have to figure out the rules, culture, and magic systems, etc.
One common theme is self - discovery. The female protagonists often have to figure out who they are in a new world. Another is romance, as they usually interact with various male characters. Power dynamics is also a theme, like when the protagonist has to deal with the power structures in the new world.
Another theme is adaptation. These characters are usually thrown into a completely different world with different cultures, magic systems, etc. So they have to adapt quickly to survive. Like in many isekai light novels, they may have to learn how to use magic or deal with strange creatures.
A common theme is starting over. The protagonist often gets a second chance at life in a different world. Another theme is power - up. They usually gain new abilities or powers in the isekai world. For example, in 'Sword Art Online', Kirito becomes a very powerful swordsman. Also, exploration is a theme. The characters explore the new and strange isekai world.
Well, love and relationships are also common themes. It could be the love for their new friends or even a romantic relationship. In addition, the theme of changing the world or the status quo is present. The mom characters often bring new ideas from their previous life and try to implement them in the isekai world, whether it's about improving education, healthcare or just general living standards.
The theme of harem or multiple relationships also exists in some 'op isekai light novel'. The OP male protagonist often attracts female characters. In 'In Another World With My Smartphone', the main character has multiple female companions around him. This adds a romantic or relationship - based sub - plot to the overall story of the isekai adventure and power growth.
One common theme is self - discovery. Protagonists are often thrust into a new world and have to figure out who they are in this new context. Another theme is power - building. They usually start from a weak state and gradually gain strength. For example, in 'That Time I Got Reincarnated as a Slime', the slime protagonist slowly builds an entire nation around him.
Survival is also a major theme. Since they are in a strange isekai world, they need to use their assassin - like skills to survive. In 'Re:Zero − Starting Life in Another World', Subaru has to constantly figure out ways to stay alive in the face of many threats.
Survival is also a big theme. Iori is usually thrown into a world full of danger, and he has to figure out how to stay alive. This involves things like finding food, shelter, and avoiding powerful enemies. Additionally, there's often a theme of friendship or camaraderie as Iori teams up with other characters in the isekai world.
Power - up is a common theme. The protagonists usually start from a weak state in the new world and gradually gain power through various means, like training or getting special abilities. Another theme is harem. Often, the male protagonists are surrounded by multiple female characters who are attracted to them for different reasons.