Perhaps the fanfiction could revolve around a time when Serena's mom was also a young trainer. Ash somehow travels back in time and meets her. They team up for a Pokemon adventure. During this, Serena's mom might see some of Ash's qualities that remind her of Serena in the future. This experience could then have an impact on how Serena's mom raises Serena later on, creating a sort of circular connection in the story.
One possible plot could be that Serena's mom discovers Ash's true potential as a Pokemon trainer and decides to help him in his journey. Maybe she has some old Pokemon training techniques that she imparts to Ash, which helps him win a big tournament.
It could be a powerful Pokemon trainer who is jealous of Ash's connection with Serena's mom. This trainer might try to disrupt their relationship and stop Ash from getting any help or knowledge from her.
One possible plot development could be that Ash and Serena have to deal with the new responsibilities of having a baby. This might cause some tension between them as they figure out how to balance their own goals and the needs of the family. Lemon could be involved as a support system, or perhaps as a source of conflict if there are romantic feelings involved among the three. For example, if Lemon has feelings for Ash, Serena's pregnancy could make those feelings more complicated.
Maybe in this fanfiction, Ash has been planning the proposal for a long time. He enlists the help of all their Pokémon friends. Pikachu holds the ring in its tiny paws. Ash takes Serena to a place that holds special memories for them, like the place where they first met. He then gives a heartfelt speech about their journey together and how he wants to continue it as her partner forever before popping the question.
Their relationship would become more mature. They would have to rely on each other more than ever. With a baby, they'd have to share responsibilities, which could lead to a deeper understanding and respect for each other.
In a fanfiction, Ash and Serena might explore their auras together. Serena, having a more refined sense of aura, could teach Ash how to better control and understand his. This could lead to a series of adventures where they use their auras to communicate secretly and solve mysteries in the Pokemon world.
One possible plot could be that they accidentally get drunk while trying some new berry juices that they thought were non - alcoholic. They start sharing their deepest dreams and fears. Ash might talk about his goal to become a Pokémon Master in a more emotional way, and Serena could open up about her insecurities regarding her performance in Pokémon showcases.
One possible plot could be that they accidentally drink something that makes them drunk at a festival in a new region they are visiting. They start acting silly, like Ash trying to show off his Pokémon skills in a very clumsy way and Serena giggling uncontrollably. Then they might share some deep secrets or feelings they've been holding back, leading to a stronger bond between them.
Well, it could be that Ash finally realizes his deep feelings for Serena during a grand Pokemon event. Maybe they are in a beautiful, flower - filled meadow near a Pokemon Center, and Ash gets down on one knee with a Pokemon - themed ring, perhaps made from a shiny Pokemon scale or something unique.
One idea could be that Ash and Serena meet again after years apart. Ash has become a Pokemon Master and Serena has achieved great success as a Pokemon Performer. They decide to travel together again, this time not just for their own goals but to explore new regions and discover new Pokemon species together. Along the way, they face challenges from Team Rocket who have a new evil plan. Their relationship deepens as they support each other through these difficulties.
One possible plot could be that their daughter discovers a hidden power within herself. Maybe she has an affinity for a type of Pokémon that neither Ash nor Serena had a special connection with. For example, she might be able to communicate with Ghost - type Pokémon in a unique way. This could lead her on an adventure to figure out where this power came from and what she's supposed to do with it.