Well, reactions to RWBY Death Battle fanfiction can vary greatly. Some might be excited about the unique battles and character match - ups depicted in the fanfiction. It could bring out new perspectives on the RWBY characters' abilities and how they would fare against each other in different scenarios. For example, seeing how Ruby's speed and scythe skills compare to another character's powers can be really thrilling.
One interesting 'Death Note Reaction Fanfiction' could be about the characters' reactions when they first discover the Death Note. For example, Light's initial shock and then his quick realization of the power it holds. Another might focus on how L reacts to the existence of the Death Note and Light's actions. There could also be fanfictions that explore the reactions of secondary characters like Misa when she gets involved with the Death Note's power.
One interesting 'death battle reaction fanfiction' story could be where characters from different universes react to a fight they never expected. For example, superheroes from Marvel reacting to a battle between anime characters. They might be shocked at the unique powers and fighting styles.
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.