One idea could be a friendly competition between Dawn and Serena over who can help Ash catch the most rare Pokémon in a new region. They might set different strategies and use their unique skills to outdo each other while still remaining friends.
A possible plot could be that Dawn and Serena are both in a race to be the first to reach Ash who has gone off on a dangerous mission alone. Along the way, they face various challenges and have to team up at times. But their underlying competition to be the one to reach Ash first remains, and when they finally do find him, they both realize that their friendship with Ash and with each other is more important than any rivalry.
The plot could be centered around academic competitions. Ash and Dawn might be the top students in one subject while Serena excels in another. They end up in a face - off during a school - wide academic decathlon. Ash and Dawn rely on their combined knowledge and teamwork, while Serena uses her own unique study methods.
In this kind of fanfiction, it could be about a rivalry in high school. Ash and Dawn might be a team or a couple, and Serena is their rival. Maybe it's a battle of skills like Pokémon battles or a competition for popularity. For example, they could be competing in a school - wide Pokémon tournament, and Serena has some new strategies that Ash and Dawn need to counter.
A possible plot is that Ash is completely oblivious to Serena's yandere nature at first. Serena starts leaving little gifts for Ash that are laced with a hidden meaning only she understands, like a charm that she believes will keep him close to her. As the story progresses, Ash begins to notice Serena's strange behavior when she gets extremely jealous over small things, like when he just has a friendly chat with a female Pokemon. This leads to a conflict within their relationship as Ash tries to figure out what's going on with Serena.
One idea could be that they embark on a new adventure in a region neither has visited before. They face unique Pokémon and challenges together, which strengthens their bond. For example, they might come across a rare Pokémon that is said to only appear to those with a strong connection. As they work to catch it, they realize their feelings for each other have deepened.
Perhaps the child gets lost in a mysterious forest while trying to follow in their parents' footsteps as a Pokémon trainer. Along the way, they meet various Pokémon that help them find their way back, teaching the child about friendship and the bond between humans and Pokémon. The child could also learn some new skills from these Pokémon encounters.
One idea could be Ash and Serena having a child who shows an extraordinary talent for Pokémon battles at a very young age. The story could focus on how they train and guide their child, just like how Ash was trained by his mentors. Another plot could be them facing a new and powerful villain who threatens their family, and they have to work together with their Pokémon to protect their home and each other.
Perhaps in the fanfiction, Ash and Dawn find a group of Pokémon that are being mistreated by a cruel trainer. They decide to rescue these Pokémon and in the process, they have to outwit the trainer and his goons. They also find a special Pokémon egg during this adventure. As they continue their journey, they take turns protecting the egg and learning more about the bond between a trainer and their Pokémon as they wait for the egg to hatch.
Well, perhaps in the fanfiction, Serena could design her own wedding dress inspired by her Pokemon performances. Ash, on the other hand, might get some advice from his old friends like Brock on how to be the perfect groom. And they could have a wedding ceremony where all their Pokemon use their special moves to create a beautiful display in the sky.
In a more elaborate plot, Ash crossdresses as Serena to infiltrate an all - female Pokemon trainer's secret society. Serena coaches him on how to act like her. As he delves deeper into this society, he uncovers a plot that threatens the entire Pokemon world. He then uses his skills and the element of surprise (since no one expects 'Serena' to be so battle - savvy) to save the day.
One idea could be that Ash and Serena travel back to the beginning of Ash's Pokémon journey. They could use their knowledge of future events to help Ash catch even more powerful Pokémon right from the start. For example, they might know where to find a rare Pikachu variant and help Ash catch it, changing the whole dynamic of his early battles.