One possible plot could be that the female Charizard has a special ability that no other Charizard has. Ash discovers this during a tough battle, and they form an even deeper bond as they train together to master this new ability.
Maybe the female Charizard gets separated from Ash in a strange new region. Ash then has to go on a journey to find her. Along the way, he meets new Pokémon and trainers, and when he finally finds his Charizard, they have to work together to overcome a powerful enemy that has been causing trouble in that region. This journey of separation and reunion could be full of adventure, growth, and strengthening of their relationship.
In a fanfiction, it could be that the female Charizard falls ill with a mysterious disease. Ash is desperate to find a cure. He travels to different Pokémon healers and even to some ancient ruins in search of a remedy. This plot could explore Ash's determination and love for his Charizard, as well as show how their relationship is not just about battles and training, but also about caring for each other in difficult times.
One possible plot twist could be that Charizard was actually trying to protect Ash by leaving. Maybe it discovered a great danger that was coming and thought that by leaving, it could draw the danger away from Ash and his other Pokémon.
The plot might involve Ash starting his journey all over again, but this time with a Charizard as his very first Pokémon. Since Charizard is a powerful and somewhat stubborn Pokémon, Ash would have to learn how to handle it right from the start. He could face challenges like other trainers trying to steal Charizard because of its rarity. Ash would have to prove his worth as a trainer and his connection with Charizard to keep it by his side.
The plot could be that Ash is orphaned at a young age and Charizard finds him. Charizard then decides to raise Ash in the wild. Ash grows up learning survival skills from Charizard and how to communicate with other Pokémon directly.
The plot could be that Ash enters a Kalos - only Pokémon competition with Charizard. They face strong opponents with unique Kalos Pokémon. Charizard might learn new moves by observing the local Pokémon. For example, it could see a Delphox use a powerful fire - type move and try to adapt it to its own style.
The plot might revolve around Ash leaving Charizard because he believes Charizard has a greater purpose elsewhere. For example, there could be a group of wild Charizard in need of a leader, and Ash realizes that his Charizard is the one. So he leaves it to fulfill that role. In the fanfiction, we could see Charizard initially being reluctant but then gradually accepting its new destiny and leading the group in a new and better way.
One possible plot could be that Ash's Charizard is revealed to be female in a special way. Then, as they journey together, they develop a deeper bond that goes beyond the typical trainer - Pokemon relationship. Maybe there are some challenges they face where the female Charizard's unique abilities or personality traits play a crucial role in helping Ash and his friends.
One possible plot could be that Ash is forced to give up Charizard in a high - stakes Pokémon battle. Maybe a powerful trainer challenges Ash and demands Charizard as the prize if he loses. Ash, being a proud trainer, doesn't expect to lose but due to some unforeseen circumstances, like a new and unknown Pokémon move used by the opponent, he loses the battle. Charizard, being sent to the new trainer, initially resists but is somehow forced to obey. This makes it seem like Charizard has betrayed Ash as it has no choice but to follow the new trainer's commands.
Well, perhaps Ash has returned to Kanto for a Pokemon tournament. As he's exploring the old stomping grounds, he stumbles upon Charizard who has been living in the Charicific Valley. At first, Charizard is a bit hesitant, but then it recognizes Ash. They then go on a journey together through Kanto, revisiting old friends like Brock and Misty, and along the way, they have to deal with some rogue Team Rocket members who are up to their old tricks. This reunion rekindles their unbreakable bond.
Well, it could be about Charizard being Ash's really loyal and powerful companion in some epic Pokémon adventures. Maybe they face off against some super-strong villains and Charizard uses its fire - type moves to save the day for Ash.
A plot twist could be that Charizard evolves during the battle. This would give it new powers and abilities, completely changing the course of the fight. It would be a huge shock to Tobias and would add a new level of excitement to the fanfiction.