Perhaps the story could revolve around a time - traveling character who ends up in the BlazBlue world and unknowingly creates a harem. As he tries to find his way back home, he has to deal with the feelings of the female characters he has befriended, like Noel, Rachel, and Taokaka. Each of them has their own reasons for being attracted to him, and exploring those reasons could be an interesting plot point.
One idea could be that the main character, a new fighter in the BlazBlue universe, suddenly finds himself surrounded by various female characters who are all intrigued by his unique fighting style. They start to vie for his attention, leading to comical and heartwarming situations.
A plot could revolve around Rachel's past. Maybe she discovers something about her family or her own origin that she didn't know before. This could lead to a journey of self - discovery. Or perhaps she has to deal with a threat to her kingdom that requires her to use both her wits and powers. For example, an ancient evil awakens and she has to gather allies and find a way to defeat it while also protecting her people.
Maybe a fanfic where Jubei takes on a young apprentice. This could show his mentoring side and how he imparts his knowledge and skills. You could include scenes of training, as well as the apprentice getting into trouble and Jubei having to rescue them, all while teaching important life lessons.
One idea could be a crossover with another popular fighting game series like Street Fighter. Characters from both universes could meet in a strange dimension and have to battle it out to find a way home. For example, Ragna from BlazBlue and Ryu from Street Fighter could have an epic showdown.
A possible plot could be that there is a strange energy disturbance that starts to merge the three universes together. Characters like Ragna from Blazblue, the Persona users, and Team RWBY find themselves in a strange new world that is a mix of all three. They must figure out what is causing this and how to stop it. Maybe there are also new enemies that are created from the combination of the different mythologies and technologies of the three universes. For instance, Grimm with the ability to use Persona - like powers or Blazblue - style Ars Magus. It would be a great opportunity for character development as they learn to work together despite their differences.
One idea could be that Aladdin, after becoming a prince, has to deal with various princesses from different lands who are all attracted to him for different reasons. Maybe some are charmed by his heroic deeds, others by his newfound wealth and status. Another plot could be that the genie accidentally creates a situation where multiple female characters from Agrabah develop feelings for Aladdin at the same time, leading to a series of comical and romantic misunderstandings.
One idea could be that the main character uses his unique skills from the Assassination Classroom to protect the girls in his harem from other threats outside of the classroom. For example, a new group of assassins comes to town and he has to keep his harem safe while also dealing with school life.
One idea could be that the main character has to go through a series of challenges in the academy, and during each challenge, he gains the admiration and affection of a different female character. For example, in a combat trial, he shows great courage and skill, which catches the eye of a strong - willed female knight - in - training. Another plot could revolve around a mystery within the academy that the main character and his harem have to solve together, bringing them closer in the process.
A really interesting plot could be that Harry's harem is from different magical cultures. One is from a tribe of magical elves, another from a far - off wizarding land with unique magic. They all come together with Harry and combine their magic to create a new, powerful spell to defeat an ancient evil that is rising again in the wizarding world. This would involve exploring different magic systems and how they interact.
One idea could be that Naruto, in an alternate universe, is a powerful leader and Konan along with other female characters from the Naruto world are drawn to his leadership and kind heart. They form a sort of harem around him, and together they face new threats to the ninja world that require their combined skills and powers.
Perhaps the story could be about a ninja who inherits a powerful doujutsu that has some sort of connection to the female characters in Naruto. As he tries to master this doujutsu, these female characters are drawn to him. They end up training together, and during their training, they discover secrets about the doujutsu and their own pasts. This could lead to a series of exciting adventures and the development of deep relationships among them.