Greninja might develop better control over its powers. In the fanfiction, it could start with some wild and uncontrolled water attacks, but with Delphox's help and the challenges they face, it hones its skills. Delphox, on the other hand, could develop a stronger sense of loyalty. Initially, it might be more focused on its own performance, but as it battles alongside Greninja, it realizes the importance of teamwork and loyalty to its partner.
One possible development for Greninja is that it could learn new techniques from Delphox. For instance, by observing how Delphox uses its psychic powers to manipulate fire, Greninja could find a way to use its water attacks in a more strategic and precise way. For Delphox, it could become more humble. When Greninja shows off some amazing feats with its speed and agility, Delphox might realize that there are always things it can learn from others and become less prideful.
Greninja could become more patient. Maybe at the start it's always eager to jump into battle, but through its experiences with Delphox, it learns to wait for the right moment. For Delphox, it might become more empathetic. Since Greninja has a different fighting style, Delphox could learn to understand and adapt to it.
Well, it could be a story about their adventures together. Maybe they team up to face a powerful enemy in a tournament. Greninja's speed and combat skills combined with Delphox's powerful fire - based attacks would make them a formidable team.
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.
It's possible that Greninja's return is part of a prophecy in the Alola region. The local people might see Greninja as a sign of great change or a hero. So Ash and Greninja have to work together not just to battle but also to fulfill this prophecy, which could involve saving the Alola region's natural balance or something similar.
As a Mew fan, Ash might start to study different aspects of Pokémon lore more deeply. This could make him wiser in the ways of Pokémon. He could also develop a more empathetic side towards Mew - like Pokémon, seeing them as not just creatures to battle with but also as beings with their own unique qualities and stories.
Ash could become more understanding of different training methods through Daisy. Maybe he learns from her how to better communicate with his Pokemon on an emotional level.
Serena's character development could be profound. First, she'd probably experience a great deal of grief. But through that grief, she could transform. She might become more fearless in battles, using Ash's sacrifice as motivation. Also, she could develop leadership qualities. Since Ash is no longer there to lead in some situations, she has to step up. She may also form new alliances and friendships as she tries to cope with the loss and move forward in the Pokémon world.
Another popular trope is the 'mystical connection'. Some fanfictions explore a special, almost magical connection between Delphox and Greninja. This could be related to their elemental powers or some ancient Pokemon lore. It adds an element of mystery and intrigue to the story, making it more engaging for readers.
Ash could become more mature. In a love - centered fanfiction with Cynthia, he might start to think more about the future and less about just the next Pokémon battle. His relationship with Cynthia could make him more strategic as he learns from her.
There could be unfinished business between them. They might have a shared goal that they haven't achieved yet. Greninja's return to Ash in the fanfiction could be to finally complete that goal, whether it's winning a particular Pokemon tournament or saving a certain place from destruction.
Well, in Alola, the battle environment is different. Ash Greninja has to adapt to the new battle rules like Z - Moves. It may start by observing local battles and learning from them. It could also adapt to the more friendly and less intense battle atmosphere compared to other regions. This means it might have to change its battle strategy a bit, not always going all - out from the start. And it might interact with different types of Pokemon that are native to Alola, which could lead to new friendships or rivalries, further shaping its adaptation to the Alola environment.