Perhaps Naruto, as an Uchiha, has a mission to retrieve a powerful artifact that has ended up in the Soul Eater world. There he meets Moka and at first they are at odds because of their different goals. But as they face various challenges together, they start to understand and respect each other, and eventually fall in love. Their relationship could then be the driving force to overcome the final obstacle, which is a powerful demon that wants the artifact for itself.
A possible plot could be that Moka is on a quest to find a way to control her inner vampire better. She travels to different dimensions and lands in the Naruto world where she meets Naruto, an Uchiha. Naruto, having dealt with his own inner demons like the Nine - Tails, can offer her some advice. They form a bond and together they explore ways to combine their powers, like using Naruto's Sharingan to enhance Moka's vision during battles and Moka's vampire strength to boost Naruto's physical attacks.
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 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.
One plot idea could be Patty somehow getting transported to the Naruto world and using her Soul Eater abilities to fight alongside the ninjas. For example, her weapon skills could be a great asset in battles against the Akatsuki.
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.
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 that Naruto, with his kitsune powers, and Moka end up in a parallel dimension where they have to work together to find a way back home. They face strange creatures and have to learn about each other's abilities along the way.
One idea could be a story where Death the Kid has to team up with a character from Soul Eater to face a new, powerful enemy that threatens the balance between the world of humans and the world of demons. They might start off not getting along due to their different personalities and ways of doing things, but as they face challenges together, they learn to respect each other and combine their strengths to defeat the foe.
One plot idea could be that Eruka somehow gets transported to the world of Free! and has to adapt to the new environment. Maybe she meets a character from Free! who is intrigued by her magic abilities from Soul Eater.
One plot idea could be Tsugumi and Akane having to team up for a special mission in the Soul Eater world. They start off not getting along well but as they face various challenges, like powerful kishin eggs, they gradually develop a deeper understanding and friendship that could potentially turn into more. Another idea is a time - travel plot where they are sent back in time and have to rely on each other to get back to their own time while also learning secrets about their families' pasts in the Soul Eater universe.
Naruto, being his energetic and determined self, would likely be very curious about Moka. He would probably approach her with his usual friendly demeanor. Moka, on the other hand, might be a bit cautious at first, but Naruto's charm could break the ice. They could start by sharing their stories, Naruto about his ninja training and Moka about her life at the DWMA. Their interactions would be filled with moments of mutual learning, as they come from very different backgrounds.