In the 'litch king story', the litch king is likely the central character. There could be other characters such as the farmers who grow the litchis in his kingdom. They might be important as they are the ones who provide the litchis that are so central to the story. And there could be a wizard or a sage who gives advice to the litch king on how to protect the litchi trees from diseases or pests. Without more information, these are just educated guesses.
I'm not sure specifically which 'litch king story' you are referring to. There could be many fictional stories with such a name or it could be a very unique and personal story. Maybe it's about a king who has some special connection with litchis? Without more context, it's hard to tell the exact story.
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.
Asta is still alive in the manga. The story keeps evolving with him at the center of the action. There have been many difficult situations, but he manages to overcome them without dying.