Well, it could be a story of rivalry at first. Pikachu is quite popular among trainers and other Pokemon, while Mimikyu is often overlooked or feared. Mimikyu might envy Pikachu's status and decide to challenge it to battles. But during these battles, they start to understand each other better. Pikachu realizes that Mimikyu is just lonely and wants some attention. So instead of fighting, they end up working together to help other Pokemon in need. For example, they might save a group of Pichu from a landslide by using their combined electric powers.
Perhaps it could be a fanfic where Mimikyu disguises itself as Pikachu at first to get closer to other Pokemon. But Pikachu discovers the truth. Instead of being angry, Pikachu feels sorry for Mimikyu. Pikachu then takes it upon itself to introduce Mimikyu to other Pokemon in a positive way. They go on adventures around the Pokemon world, visiting different regions. Along the way, they meet new Pokemon friends, and Mimikyu slowly gains confidence in showing its true self, all thanks to Pikachu's friendship and support.
Well, it could be about Pikachu befriending Mimikyu. Maybe Pikachu discovers that Mimikyu is not as scary as it looks under that disguise. They could go on adventures together in the Pokemon world, like exploring a new forest or finding a rare Pokemon.
One plot twist could be that Mimikyu's disguise is actually a magic spell that was cast on it by an evil Pokemon, and Pikachu has to find a way to break the spell.
Here's a plot idea. There's a new Pokemon trainer in town who only wants to catch Pikachu and Mimikyu. They keep running away from the trainer and end up in an old, abandoned Pokemon sanctuary. There, they find out about the history of the place and some secrets about their own species. They also meet some old and wise Pokemon who teach them new moves. Eventually, they outwit the trainer and decide to stay friends and protect the sanctuary from any harm in the future.
For Pikachu, remember it's energetic and friendly. It often shows its emotions through its electric shocks, like when it's excited or scared. Pikachu loves to play and is very loyal to its trainer. Mimikyu, on the other hand, is a bit more mysterious. It's shy because it's self - conscious about its appearance. It hides under its disguise. Mimikyu can be a bit envious at times but also has a big heart deep down.
Mimikyu has the ability to create illusions. In the fanfic, it could use this ability to protect Pikachu. For example, when a powerful and dangerous Pokemon attacks them, Mimikyu could create an illusion of a much stronger Pokemon to scare it away. Pikachu's electric abilities could be used to power up Mimikyu's illusions, making them more realistic. They could also use their combined skills to solve puzzles. Say there's a maze that is protected by electric barriers. Pikachu could discharge electricity to temporarily disable the barriers while Mimikyu creates an illusion of the correct path for them to follow.
The fanfic could be about Pikachu getting angry when a new powerful Pokemon arrives in the area and starts bullying the other Pokemon. Pikachu, being the brave little Pokemon it is, stands up to the bully. At first, it loses battles due to its anger getting the best of it. But with the support of its friends, it manages to channel its anger into strength and defeats the bully.
Friendship is a very common theme. Since Mimikyu is often a bit of an outsider and Pikachu is so well - known, many fanfics focus on how they can become friends despite their differences.
One possible plot could be that Pikachu is exposed to a rare type of thunderstone during a powerful thunderstorm. This thunderstone has been charged with an ancient energy. Pikachu absorbs this energy and begins to evolve. But instead of evolving into Raichu right away, it goes through a series of strange and new intermediate forms, each with unique powers. As it evolves, Pikachu has to learn to control these new powers while also facing challenges from other Pokemon who are either jealous or see it as a threat.
A fanfic could be centered around Ash exploring a new region where Mimikyu is said to be very common. Ash is eager to add a new and different Pokemon to his team. He meets a local trainer who tells him all about Mimikyu's habits. Ash follows the trainer's advice and goes to a particular meadow where Mimikyu likes to play. He waits patiently until he sees a Mimikyu. Ash then uses his best Pokeball and with a little bit of luck, catches Mimikyu. Once caught, he discovers that Mimikyu has some hidden powers that he's excited to explore and train with.
It could be about their adventures together. Maybe they explore a new region, encounter other Pokemon, and have to work together to overcome challenges. For example, they might face a powerful, rogue Pokemon that is causing trouble in the forest where Bayleef usually stays. Pikachu's electric attacks and Bayleef's grass - type moves could combine in interesting ways to defeat the foe.