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.
Another theme is perseverance. The lovers usually face numerous obstacles, such as misunderstandings, family opposition, or social constraints. But they keep on fighting for their relationship, which shows great perseverance. For example, in many such novels, the couple might be from different social classes, and society looks down on their relationship. But they still strive to be together.
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 popular cinta sengsara romantic novel could be 'Love in the Midst of Sorrow'. It often tells a story of two lovers facing various hardships but still holding onto their love.
A third theme could be the power of place. London, with its iconic landmarks and unique atmosphere, could play a significant role in the relationship. The love story could be centered around how the city itself influences the characters' feelings for each other. Maybe the rainy London days bring them closer or the grandeur of Buckingham Palace makes their love seem more special.
I'm not sure exactly what 'cerita cinta london love story' is. It could be a very personal or a local story. Maybe it's about two people who met in London and fell in love. They might have met at a famous London landmark like Big Ben, and then their love story unfolded as they explored the city together.
Some specialized online novel websites might be a good place to look for 'titian cinta online novel'. Websites like Wattpad are known for hosting a wide variety of user - generated and published novels. Also, Goodreads has a lot of information about different novels, and it might direct you to the right place where you can find this particular novel. It could be that the novel is available on a regional or less - known platform, in which case searching on general - purpose book - related websites can give you some leads.