Perhaps a mortal with a special gift for metallurgy or some other craft related to Hephaestus' work. This mortal could be seen as an equal in terms of skill, at least in a way that catches Hephaestus' eye. They would bond over their shared love for the craft, and over time, this bond could turn into a deep, loving relationship. Hephaestus might be drawn to the mortal's unique perspective and the way they approach the craft despite not having the same divine powers as he does.
Hinata is a very obvious choice. She has always had deep feelings for Naruto. In a fanfiction, their relationship could spiral further, exploring more of their shared interests, like their love for the village and their dreams for the future of the ninja world.
If it's a crossover with the Percy Jackson universe, Percy himself could be interested in Ruby. They both have a sense of adventure and a desire to protect their friends. Annabeth might find herself drawn to Weiss because of their shared intelligence and strategic thinking. Leo Valdez could have a crush on Yang due to her mechanical skills and fiery personality. And Nico di Angelo might be intrigued by Blake because of her mysterious nature. These could all be great potential love interests in a RWBY - Percy Jackson crossover harem fanfiction.
Ezra might also be a possibility. He could be involved in a complex relationship with Spencer where he has to deal with her pregnancy and all the emotions that come with it.
There could be an older, more mature character, like a college student who she meets by chance and who is drawn to her unique charm and innocence.
It could be a figure skater. Maybe a rising star in the skating world who Bella meets at a competition and they strike up a connection. He might be drawn to her passion for the sport.
One possibility is Neville. He has always been a kind - hearted and brave character. In the fanfiction, he could be a knight or a nobleman who has a secret admiration for Hermione. As she becomes a princess, he might finally gather the courage to approach her. Or perhaps a wizard from a far - off land, who has heard of Hermione's intelligence and beauty and travels to court her. This wizard could bring new magic and different perspectives into Hermione's life, and a potential love story could unfold between them.
Sakura could be a potential love interest. Since Naruto has always had a connection with her, as a girl, that connection could turn into a yuri - like romantic relationship. They already know each other well, and Naruto's new form could make Sakura see her in a different light.
Akeno could also be a possibility. Her calm and sometimes mysterious nature might draw Kaido in. Their interactions could start with mutual respect due to their combat abilities and develop into something more romantic over time.
One potential love interest could be Joey. They could have a different kind of dynamic as Yugi is a girl. Maybe Joey is initially protective of her and then gradually falls in love. Their relationship could be based on mutual respect for each other's dueling skills and shared experiences in the Duel Monsters world.
Jacob could be a potential love interest. He's a werewolf, and his connection to Sam's pack could bring an interesting dynamic. Their relationship could start off as a friendship based on mutual understanding of the supernatural world, and then develop into something more romantic over time.