I'm not sure specifically as there could be many novels with this title or related to this phrase. It might be about a story where the protagonist is transported to another world ('isekai' means another world in Japanese), perhaps with adventures, magic, and new characters.
Writing fanfic that involves sexual content is generally not appropriate as it can violate ethical and moral boundaries, and may also go against the terms of use of certain platforms. Moreover, it objectifies the characters in an improper way.
Among the few novels, there were two novels that involved the use of the tachi," Saving Uchiha begins with being a patriarch " and " The Remnant Fire Tachi of the Wood Leaf." " Saving Uchiha from Being a Clan Leader " was a story about an individual who had inherent skills and many precious artifacts who started his adventures in anime. However, this novel did not focus on the use of a tachi. In contrast," Koba no Kagami Tachi " focused on the use of a tachi. The protagonist, Yusuke, transmigrated into Naruto and started off with a tachi. Later, in his conversation with Uchiha Weasel, he also mentioned the use of a tachi. Therefore, I strongly recommend [Muye: Remnant Fire Tachi] to you! I hope you like my recommendation.😗
The 'isekai kara kita yuusha novel' likely tells a story full of fantasy elements. The hero coming from another world is a common trope in isekai stories. He could be summoned there by some magic or accident. Once in this new world, he may have to adapt to different cultures, magic systems, and races. His experiences would form the core of the story, which might include battles against powerful foes, exploring unknown lands, and uncovering the secrets of this new world.
One common theme is friendship development. Since kita and bocchi are often characters in a story, their friendship might be explored in depth, showing how they get to know each other better over time.
The 'Mondaiji Tachi' in both anime and novel has a fascinating world - building aspect. The concept of the 'Gift Games' is central. These games are not just simple competitions but are deeply intertwined with the characters' abilities and the overall plot. The novel delves deeper into the backstories of the characters, while the anime focuses more on the visual representation of the action - packed scenes, especially during the Gift Games.
There's no easy way to determine the popularity of'mondaiji tachi visual novel' without more information. Some visual novels gain a cult following, while others remain relatively unknown. It could be that it has a dedicated but small group of fans who love it for its unique take on the'mondaiji tachi' world, or it could be that it has managed to break out and gain a wider audience. However, without looking at things like review scores, social media presence, and sales figures, we can only speculate.
"I recommend Monster Hunter's Hunt." It's a novel about a different world. The main character carries a katana made from ancient dragon material and fights for the honor of the hunter. I hope you like my recommendation. Muah ~
I'm not aware of a specific work titled exactly 'isekai ni kita novel' being extremely popular. But there are many popular isekai novels in general, like 'Sword Art Online' which has some elements of being transported to a different world.