By showing their shared history. Flashbacks to their early days together can add depth. For example, remember when they first met? That could be a great starting point to build on their relationship in the fanfic.
Their relationship could be developed through shared interests. For example, both are interested in unique and delicious food. Bulma could cook special dishes for Beerus, which would gradually make Beerus see her as more than just an ordinary Earthling. He might start to respect and even protect her in return.
It can start with them having simple conversations. For example, Kakarot asking Bulma about her latest inventions. This can gradually lead to a deeper connection as they start to understand each other's dreams and fears.
He could break her heart by cheating on her. Maybe he gets involved with another woman, and when Bulma finds out, she is devastated.
For Yamcha, you can focus on his growth from being a bit of a comical character to a more serious and respected fighter in the context of his relationship with Frieza. Maybe he learns from Frieza's cold and calculating nature how to better strategize in battles. For Frieza, his development could be about him learning to care for someone other than himself. He could start to see Yamcha as an equal, which is a huge shift from his usual superiority complex.
Their relationship can be developed through shared adventures. For instance, when they go on a quest to find a lost relic. During this adventure, they rely on each other's skills, which builds trust.
It could start with a mutual respect for each other's abilities. Naruto might admire Tayuya's musical based attacks, and Tayuya could be intrigued by Naruto's never - give - up attitude.
By showing their shared history. Maybe start with a flashback of their childhood together, how they were friends or rivals from the start. This can set the foundation for their complex relationship in the present of the fanfic.
Another way is through a common enemy. Suppose a new dark force emerges that threatens both Tikal's spiritual realm and Chaos's domain. They are forced to put aside their initial differences and work together. During this process, they start to communicate more, share their feelings and fears. Tikal helps Chaos to control its power better, and Chaos gives Tikal the strength to face the new threat, thus strengthening their relationship.
In a fanfic, their relationship could develop through a series of magical duels. Each duel is not just about fighting but also about learning about each other. Harry might learn about Bellatrix's past that made her the way she is, and Bellatrix could be impressed by Harry's growth as a wizard. This understanding gained from the duels could lead to a more complex relationship between them.
Another way is through an accidental encounter that leads to a series of events. Let's say Darkrai accidentally enters Cressila's territory while fleeing from a group of hunters. Cressila is initially angry but realizes that Darkrai is in trouble. It decides to help Darkrai hide. During this time, they start to communicate. Darkrai is intrigued by Cressila's kindness, and Cressila sees that Darkrai is not as bad as it seems. From there, their relationship blossoms as they continue to interact and face new challenges side by side.