One plot idea could be Cardin trying to balance his relationships within the harem. For example, he might have to deal with the different personalities and needs of each member. Another could be the harem facing a common enemy together, which would strengthen their bonds. Maybe there could be a plot where a new character enters the harem and causes some jealousy and drama among the existing members.
Well, a cool plot idea for a RWBY Cardin harem fanfiction could be that Cardin discovers that each member of his harem has a unique power or ability that, when combined, can unlock an ancient and powerful secret. As they go on a quest to figure out this mystery, they also have to deal with the normal relationship stuff like dates, arguments, and making sure everyone feels included. And also, perhaps there's a rival group that wants to break up the harem to get at this power for themselves.
A possible plot idea is that Cardin's harem is formed because of a strange magical event at Beacon Academy. At first, he's really confused and not sure how to handle having so many girls interested in him. But as time goes on, he realizes that they all have their own reasons for being part of the harem. Some might be there because they see a different side of him, others might be drawn to his strength. And then they all have to work together to keep their harem a secret from the more strict teachers at the academy while also growing closer as a group.
Velvet could be a potential member. She's kind - hearted and might be attracted to Cardin's more confident side. Another could be Pyrrha. She's always looking for new relationships and experiences, and Cardin's unique personality could draw her in. And Coco could also be in the harem. She's bold and might see Cardin as an interesting challenge.
Maybe a powerful and mysterious force affects the minds of some RWBY characters, turning them into yanderes for a particular character. This could lead to a lot of drama as they try to keep their yandere tendencies hidden while also vying for the object of their affection. For example, Ruby could be affected and her normally innocent nature takes on a more possessive and obsessive side when it comes to the person she loves.
The gamer OC could be from our world and is somehow sucked into the RWBY world. In this new world, he realizes that his knowledge of games gives him an edge. He starts to form a harem as he helps the RWBY characters in different ways, like providing strategic advice during battles. For instance, he might suggest new ways to fight the Grimm based on his gaming experience. The relationships in the harem could develop as they train together and the OC shows his determination and kindness. Some characters might be initially skeptical of him but gradually warm up due to his positive influence.
Maybe it could be about Cardin trying to hide his Faunus identity at first. He might struggle with the discrimination that Faunus face in the RWBY world while also dealing with his own personal growth and relationships within the team or at school.
One idea could be a crossover with another popular anime like Naruto. The RWBY characters could find themselves in the Naruto world and form relationships with the Naruto characters, creating a harem dynamic. For example, Ruby could befriend Naruto and his friends, and some of them might develop romantic feelings for her over time. Another idea is a crossover with a game world, such as the Elder Scrolls. The RWBY girls could explore the vast lands of Tamriel, meet different characters, and have a harem of followers or admirers from different races in the game. Maybe Weiss could attract the attention of some noble elves or powerful mages in Skyrim.
One idea could be that the male reader is a transfer student to Beacon Academy. He has a unique Semblance that catches the attention of the RWBY girls. For example, his Semblance could be related to time manipulation. Ruby might be intrigued because she loves unique abilities and wants to learn from him. Weiss could initially be a bit standoffish but as she sees his skills and determination, she warms up to him. Blake would see something in him that reminds her of her own struggles, and Yang would be attracted to his confidence.
One common theme is redemption. Many fanfictions focus on Cardin realizing his wrongdoings and trying to become a better person. Another theme is friendship. Some stories show Cardin forming unexpected friendships, like with members of Team RWBY.
One idea could be Noctis arriving in the RWBY world and having to learn about Dust and how to use it in combat. Maybe he teams up with Team RWBY to fight against a new type of Grimm that his unique skills are well - suited to defeat.
One idea could be a mercenary who is hired by a mysterious client to steal an ancient relic from Beacon Academy. He has to navigate through the various defenses and teams of Huntsmen and Huntresses.
One idea could be a new student arriving at the school with a mysterious power that no one has seen before. This could cause both excitement and suspicion among the other students.