We don't know exactly when the Akatsuki no Yona manga will come to an end. It all depends on the story's complexity and the author's vision. Maybe there are still many exciting chapters to come before the conclusion.
In Akatsuki no Yona fanfiction, male OCs can add new dynamics. They might be designed as new allies for Yona and her group. For example, a male OC could be a skilled warrior from a far - off land who joins them on their journey, bringing with him unique fighting styles and cultural knowledge.
In general, the Akatsuki no Yona anime didn't fully catch up to the manga. There are still significant parts of the story in the manga that weren't included in the anime adaptation. Maybe it was due to various production considerations or limitations.
Love and relationships also play a big part. Whether it's romantic relationships between characters from different worlds or the deepening of friendships. In these fanfictions, characters often have to overcome cultural differences and the challenges of being from different fictional settings to form meaningful connections with one another.
Develop his skills and abilities carefully. If he's a great archer, explain how he got such good skills. Maybe he was trained by a hermit in the mountains. His skills should complement or contrast with the skills of the existing characters in the story.
A great place to start is Archive of Our Own (AO3). They have a wide variety of 'harry potter akatsuki no yona fanfiction'. You might find ones that explore character relationships. For example, a story could be about how a character from 'Harry Potter' with their particular set of skills and personality traits might form alliances or rivalries with characters from 'Akatsuki no Yona'.