How about a story where a kid discovers a secret garden? In this garden, there are talking flowers and friendly bugs. The kid has to learn how to take care of the garden and in return, the plants and bugs help the kid with his or her problems at school.
One idea could be a story about a magical tree house. The tree house can transport kids to different time periods or magical lands. They could meet historical figures or mythical creatures there.
One idea could be exploring MK's training in more detail. Show his struggles and how he overcomes them. For example, he might face a new and extremely powerful demon that forces him to master a new skill quickly.
Another interesting concept is a crossover with the Harry Potter universe. Picture Kid at Hogwarts. He'd probably be a bit of a troublemaker, not fitting in well with the school rules. He could form an unlikely friendship with the Weasley twins and together they'd play pranks on the Slytherins, all while Kid is trying to find a way back to his own world.
A cool Kaito Kid crossover fanfiction idea is with the world of Harry Potter. Kaito Kid could try to steal a magical artifact from Hogwarts, like the Philosopher's Stone. He'd have to navigate through the magical defenses and deal with the wizards and witches. Also, a crossover with One Piece. He might target a Devil Fruit, which would put him in conflict with the Straw Hat Pirates. And a crossover with Pokémon. He could be after a rare Pokémon that has some special power, like Mewtwo.
One idea could be a crossover with Harry Potter. Kid Goku could end up at Hogwarts and his martial arts skills would be a unique addition to the magical world. He might use his Ki blasts instead of magic spells in some situations.
One idea could be a crossover with the Teen Titans. Kid Flash could team up with them to fight a new super - villain that is causing chaos across multiple cities. His speed could add a new dynamic to the Titans' combat strategies.
One idea could be that the character relives their childhood during a magical time - like a time - traveling accident. They get to see their old friends and family members as they were, and re - experience the simple joys of childhood like playing in the park or having ice cream on a hot summer day.
One idea could be a story where Batman and Superman's kids team up to solve a mystery in Gotham City. Maybe they find a strange device that's causing chaos and they have to use their combined skills, like Batman's detective skills and Superman's super strength, to figure it out.
One idea could be a crossover with the Dragon Ball Super universe. Kid Buu could encounter new and powerful foes like Jiren. Their fight would be chaotic and destructive, with Kid Buu's unpredictable nature causing all sorts of mayhem. Another idea is a crossover with the Naruto universe. Picture Kid Buu facing off against Naruto. Naruto's positive energy and willpower could be a contrast to Kid Buu's pure evil. He might try to reason with Kid Buu at first, but when that fails, a huge battle would ensue. And a third idea could be a crossover with the One Piece world. Kid Buu might land on the Grand Line and start causing trouble for the Straw Hat Pirates. Luffy would surely step up to protect his crew and the islands they visit from Kid Buu's rampage.
Look at their daily experiences. A story could be about a kid's first day at a new school. All the nervousness, making new friends, and getting lost in the big school building. Add some magic to it, like a friendly ghost that shows the kid around.
Another interesting fanfiction could be set in a scenario where Kid Gohan has to teach Kid Videl some of his Saiyan powers. This could involve training sessions filled with funny moments as Videl tries to understand and control the newfound abilities. They could also have some friendly competitions to see who is stronger at different stages of her training.