"The Beauty Catastrophes the World" was a fantasy romance novel. It was about the female protagonist who had changed her body because of a car accident. She was hunted down by her vicious stepmother and was tested to have a useless physique. In a world where martial arts were respected, she was ridiculed and insulted wantonly. However, a useless person could also bully men and women, live a carefree and arrogant life, and harm the world! The female lead was dressed as a man. She was a little rebellious, a little extreme, a little extreme, a little cold-blooded, and a little vengeful. I'm recommending "Beauty Catastrophes the World" to you. I hope you like this fairy's recommendation. Muah ~
One idea could be a rengoku fanfic where he trains a new group of young slayers. It could focus on his unique teaching methods and how he instills his values in them.
Tanjiro would be a great character to pair with rengoku. Their different personalities could create an interesting interaction. Tanjiro's kind - hearted nature and rengoku's fiery determination could lead to some great storylines.
One of the main themes is adventure. Since rengoku is often involved in battles and dangerous situations, the fanfics may take the reader along on these adventures. They might face demons together and their relationship develops through these shared experiences. Also, loyalty is a big theme. Rengoku is a very loyal character, and this loyalty extends to his relationship with the reader in the fanfics.