Another plot could be that the reader is an outsider to the world of Soul Eater, perhaps from a different dimension. Soul accidentally discovers the reader and at first is suspicious. But as he gets to know the reader, he realizes that they are kind - hearted. They then have to deal with the challenges of the reader adapting to the Soul Eater world while also falling for each other.
One idea could be the reader being a new student at the DWMA. They could struggle to find their weapon partner at first, but then end up with an unexpected and powerful weapon. Another plot could involve the reader having a special ability that draws the attention of the Kishin's minions, leading to various battles and the need for protection from the main Soul Eater characters.
Maybe an OC that has a special ability related to time. They can slow down time briefly during a fight. But this power comes with a cost, like it drains their soul energy quickly. The fanfiction could explore how they learn to control this power and balance its use while also dealing with the normal challenges at the DWMA, such as making friends and passing classes.
One idea could be a story where the main character discovers a hidden power within their soul that has the potential to either save or destroy the world in the Soul Eater universe. They then have to struggle with the moral implications of using this power.
One plot idea could be that the reader is a new student at the DWMA and Stein takes them under his wing as an apprentice. As they work together, they start to develop feelings for each other. Another could be that the reader has a special power that Stein is intrigued by and he tries to study it, which leads to them getting closer.
One idea could be that Soul's sickness is caused by an unbalanced resonance with Maka. Maybe they've been overusing their Soul Resonance in battles and it's taking a toll on Soul. Another idea is that an enemy has cursed Soul, making him sick in a way that weakens his combat abilities and his connection to his weapon form. For example, the curse could make it painful for him to transform.
Maybe Mifune's code of honor clashes with the more chaotic and rule - bending nature of some of the Soul Eater characters. For example, he might not approve of how Black Star is so eager for glory and fame without following proper protocol. This could lead to interesting character development and story arcs for both sides.
One idea could be that Naruto characters are transported to the Soul Eater world. Naruto's determination could be a great asset in the battle against Kishin Eggs. He might use his shadow clones to surround and overpower the enemies. Another plot could involve the weapons from Soul Eater trying to learn Naruto's ninjutsu. For example, Soul could be interested in the Rasengan and try to incorporate it into his fighting style. Also, Maka's strong sense of justice would blend well with the Naruto characters' values, and they could team up to take on powerful foes together.
One idea could be an OC who has a unique weapon form that no one has seen before in the Soul Eater world. For example, an OC that can transform into a musical instrument like a harp that has the power to soothe or disrupt souls. Another plot could involve an OC who is a transfer student from a far - off place with a different type of soul wavelength training, and they have to adapt to the DWMA's methods while also teaching the others something new. A third idea is an OC who has a connection to a powerful and ancient soul that starts to cause problems as the story progresses.
Well, you could have a witch OC fanfiction where the witch is an outcast among her own kind. She doesn't believe in the typical evil ways of witches and wants to use her powers for good. So she approaches the DWMA with an offer of peace and cooperation. Another plot could be that the witch OC has a hidden lair where she collects ancient artifacts that have the power to change the balance between witches and the DWMA. And a third plot idea is that the witch OC is in love with a DWMA student, and this forbidden love creates a whole lot of drama and challenges as they try to be together in a world where witches and DWMA are usually at odds.
One idea could be a crossover where the Juubi's power somehow gets transferred to a character in Soul Eater and they have to learn to control it. Another could be Naruto getting lost in the Soul Eater world and having to adapt to their way of fighting and dealing with souls.