Cultural exchange. Mifune comes from a different background than Black Star. So, they could exchange ideas about their respective cultures, like Mifune's samurai culture and Black Star's world in Death City. This could be a central theme.
Growth. Black Star could grow from a brash and overconfident young man to a more refined and powerful fighter under Mifune's tutelage.
The theme of mentorship. Mifune as a mentor guiding Black Star. This would involve teaching him about honor, respect, and the true meaning of strength. It could also show how Black Star responds to this mentorship, whether he accepts it wholeheartedly or rebels against it at times.
I'm not sure if there are a lot of such fanfics out there. But it could be an interesting concept. Maybe in this fanfic, Mifune, with his samurai skills and honor, imparts unique combat and life lessons to Black Star. It might show how Black Star grows under Mifune's guidance, both in terms of his fighting abilities and his understanding of the world around him.
Black Star leaving could trigger a series of events. He could end up in a place full of dark magic where he has to fight to survive. Meanwhile, back in Death City, there could be an attack by an enemy who was waiting for Black Star to be gone. The remaining characters would have to step up and defend the city without him, which could be a great source of character development.
A good fanfic about them should focus on their unique relationship. Black Star's over - the - top personality and Tsubaki's more reserved nature create a great dynamic. For instance, a fanfic could play on how Black Star's boasting sometimes annoys Tsubaki, but she still stands by him.
In many Black Star fanfictions, his relationship with the other characters is a key aspect. He might have interesting interactions with Maka and Soul. Maybe there's a fanfic where they team up for a special mission and Black Star has to learn to work with them in a different way than he's used to.
Maka would also be a great character to interact with Mifune. As a strong - willed and intelligent student at the DWMA, she might be intrigued by Mifune's skills and his different approach to combat. She could try to learn from him, or even teach him some of the DWMA's ways in return.
In a fanfiction, a kiss between Black Star and Tsubaki might be a culmination of their character development. Black Star, who is often brash and confident, could show his more vulnerable side through this kiss. Tsubaki, on the other hand, might be the one to initiate it, surprising Black Star. This could lead to a whole new dynamic in their relationship. They might start to communicate more openly about their feelings, and it could also affect how they interact with their friends and other characters in the Soul Eater universe. It could be a moment that fans have been waiting for, full of passion and tenderness.
One great fanfic could be where they go on a mission together that's not part of the main story. They might face a new type of enemy that tests their bond and abilities in different ways. For example, they could encounter a demon that can split into multiple forms, forcing Black Star to rely more on Tsubaki's unique weapon forms than just his own strength.
One idea could be that Black Star leaves to pursue a solo mission to prove his strength without relying on his friends. He might encounter a powerful and mysterious foe that challenges his very core beliefs. This would make for an exciting story as he battles not just physically but also internally.
The theme of friendship also shows up a lot. Despite his brash exterior, Black Star has friends. Fanfictions may show how his friendships are tested, for example, when he has to make a difficult choice that could potentially harm a friend, and how he navigates through that moral dilemma.
In a fanfiction where Black Star becomes a weapon, his design as a weapon would probably be very unique. Given his love for being flashy and his ninja - like style, he could be a weapon that has a lot of sharp edges and a sleek, black design. Maybe he'd be a sword with some sort of special ability related to his ninja skills, like being able to disappear and reappear during combat, or having the ability to cut through dimensions.