I'm not entirely sure specifically as there could be various themes in it. It might be about a character's unique journey, perhaps with elements of mystery, action or personal growth. But without reading it, it's hard to say precisely.
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.
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.
One interesting story could be about a player who discovers a hidden path in the hitori kakurenbo game. This path led them to a special area where they found rare items that helped them progress further in the game.
Another option is to check with local libraries. Some libraries have sections dedicated to international literature or manga/light novel collections. They might have a copy of 'hitori no shita light novel' that you can borrow and read. If your local library doesn't have it, you could request them to acquire it.
The 'isekai de tada hitori light novel' could potentially be about a solitary adventure in an isekai world. It might follow the journey of a character who finds themselves alone in a strange new world, perhaps facing various challenges, making new discoveries, and growing as a person while dealing with their solitude.
I don't have information about the author of this 'isekai de tada hitori light novel' at hand. You may need to search for it in specialized light novel databases or websites.