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.
Well, in 'Mom and Me and Mom Story', the theme might be about family dynamics. It could show how the two generations of mother - daughter or mother - son interact, with all the joys, sorrows, and lessons learned in that relationship. It may also touch on forgiveness, acceptance, and self - discovery within the context of the family unit.
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.
Well, some popular rengoku x reader fanfics can be found on Wattpad as well. Look for ones with high ratings and good reviews. They usually offer different storylines, from adventure - filled ones where rengoku and the reader go on quests together, to more romantic and heart - warming stories about their relationship.