He could form a friendly rivalry with Issei. Since Issei is all about power and his Boosted Gear, and Asta is super determined with his anti - magic sword, they could compete in terms of strength and growth. They might also learn from each other's combat styles.
Goku's ultimate form in the manga is Ultra Instinct. This state grants him enhanced combat abilities and reflexes. It's a breakthrough that showcases his potential and is a key factor in his toughest battles.
Well, in some fanfictions, Asta's demon form might have a different appearance. Instead of the typical spiky look, it could be more streamlined and elegant, with a black and red color scheme that gives off an even more menacing vibe. Also, his demon form could possess the power to create illusions, which he uses to deceive his enemies. This would make him a more versatile fighter and add a new dimension to his battles.
His relationship with Sister Lily could be really interesting in fanfiction with his demon form. Since she has a kind and pure nature, she might be conflicted about Asta having a demon form. On one hand, she believes in Asta's good heart, but on the other hand, the idea of a demon form might go against her religious beliefs. This could lead to some really emotional and thought - provoking interactions between them, and Asta would have to prove to her time and again that his demon form doesn't change who he really is.
Since lemon fanfics are inappropriate, we should focus on their general characteristics from the official story. Asta is highly determined and energetic, always striving hard despite his lack of magic initially. Yuno, on the other hand, is more calm and has a natural talent for magic. They both have a strong bond as rivals and friends.
Noelle could be a great addition. Her water magic is quite powerful and she has a complex relationship with both Asta and Yuno. She could be a source of both support and conflict in the fanfic. Another good character is Luck. His lightning magic and his rather unpredictable nature can add a lot of action and excitement to the story.
Asta would likely bring a new level of determination to the Crimson Lions. His never - give - up attitude could inspire the team members during tough battles.