Perhaps the story could revolve around Serena getting lost in the alleys of Lumiose. As she tries to find her way out, she stumbles upon a group of Pokemon trainers having a unique battle style she has never seen before. This inspires her to develop her own new training techniques for her Pokemon.
Well, it could be about Serena's adventures in the alleys of Lumiose City in the Pokemon world. Maybe she encounters unique Pokemon, or has some interesting interactions with other characters. Without reading it, it's hard to say exactly what it contains, but it might explore the more hidden and less - known aspects of Lumiose through Serena's perspective.
Friendship could be another theme. Maybe Serena meets new friends or strengthens existing relationships while in the alleys. She could encounter other trainers or characters who help her on her journey, and through these interactions, the theme of friendship is developed.
There could be a young street urchin who has befriended a group of abandoned Pokemon. Serena could interact with this character and learn about the importance of kindness towards all Pokemon, even those without trainers. The urchin and his Pokemon friends could also help Serena in her journey through the alleys.
One possible plot could be Serena discovers she's pregnant during her Pokemon journey. This could bring about a lot of changes in her goals and how she interacts with her Pokemon. Maybe she has to take a break from her usual adventures to take care of herself and the upcoming baby, and her Pokemon become more protective of her.
The plot could involve Serena encountering a Hypno in the wild. Maybe she's initially scared, but then realizes Hypno has some unique abilities that can help her in her Pokemon journey. For example, Hypno could use its psychic powers to lead Serena to rare Pokemon or hidden items.
Well, it could start with Ash finally realizing his true feelings for Serena. Maybe they meet up again after a long time apart. Then they start to plan a small, intimate wedding in a beautiful Pokemon - filled location like a meadow full of Pikachu and Eevee. Their Pokemon friends could help with the preparations, like Pidgey delivering invitations.
One possible plot idea could be Serena starting a new Pokemon journey in Alola. She might encounter unique Alola Pokemon and have to adapt to the new region's battle styles. For example, she could participate in the Alola trials and learn about the local culture and traditions related to Pokemon.
Well, it could be that Serena gets a new flying - type Pokemon as her ride. Maybe it's a shiny Pidgeot that she discovers in a hidden forest. This new ride would allow her to travel faster across the Pokemon world and reach new regions more quickly for her Pokemon journey.
A Litten might be a good choice for Serena. It has a fiery personality and could bring a new dynamic to her team. With proper training, it could become a powerful Fire - type Pokemon in battles against water - type opponents in Alola.
One possibility could be that Serena gets angry when she is constantly overshadowed by other trainers in a big tournament. She might feel that all her hard work is being ignored, so she gets angry and decides to train even harder in isolation to prove herself.