Another common theme is the fish - out - of - water situation. The MC is transported to a new world, so they have to adapt to new cultures, magic systems, and social structures. In 'Konosuba', Kazuma has to deal with all the crazy things in the isekai world while trying to make the best of his situation with his OP party members. And they often have a goal, like saving the new world or finding a way back home, which drives the story forward.
Sure. 'Overlord' is a great isekai novel with an OP main character. Momonga, the protagonist, gets transported to another world and has incredible power from the start. Another one is 'That Time I Got Reincarnated as a Slime'. Rimuru starts off as a slime but quickly becomes very powerful in the new world.
Well, one common theme is the exploration of the isekai world itself. The OP characters often go on adventures, discover new places, and uncover secrets. Another is the concept of relationships. They form alliances, make friends, and sometimes enemies in the new world, and these relationships are shaped by their OP status. Also, the theme of challenging the status quo is present. Their OP abilities give them the power to change things in the world they are transported to, whether it's the political system or the way magic is used.
One popular isekai op novel is 'Overlord'. In this novel, the main character is transported to a different world with extremely powerful abilities. He has to navigate this new world while being almost overpowered compared to the native inhabitants. Another great one is 'Tensei Shitara Slime Datta Ken'. The protagonist, reincarnated as a slime, quickly gains OP (overpowered) abilities and builds his own nation in the isekai world. There's also 'No Game No Life' where the siblings are transported to a world ruled by games and they possess incredible skills and intelligence that make them OP in this new realm.
Well, it depends on the setting and rules of the visual novel. The MC might face battles against fictional enemies, have to make important choices that affect the story's outcome, or even discover hidden secrets and treasures.
The plot might get really interesting. The MC could use their knowledge from the real world to turn the tables and become a hero despite starting as an antagonist. Or they might struggle to fit in and face a lot of challenges because of their initial role.
Well, an MC novel is one where the plot mainly revolves around a particular protagonist. The actions, decisions, and growth of this main character drive the story forward. It's all about following their adventures and seeing how they handle various situations.
I need more context to answer your question. Could you please provide more information about the NPC? The " NAC-17 " standard in online literature was a grading system that restricted the content of novels. Different countries and regions may have different standards for the use of the MC-17, but most of them set limitations on the content, language, violence, horror, and other aspects of the novel.