Well, you could write a chibi Hidan fanfic where he befriends a small animal. Maybe he finds a little frog and tries to convince it that his beliefs are the right ones. Since he's in chibi form, the frog doesn't seem too intimidated and just hops around while Hidan gets all worked up. It would be a humorous take on his character.
One idea could be a chibi Hidan getting into comical misadventures in the Akatsuki hideout. For example, he might accidentally paint the wrong symbols on the walls while trying to perform some sort of ritual in his miniaturized form. Another could be chibi Hidan trying to teach the other Akatsuki members his unique view on immortality, but they just laugh at his cute, tiny self as he tries to be serious.
Well, a 'hidan sakura fanfic' could explore their relationship in a comical way. For example, Hidan accidentally gets a curse that makes him see Sakura as the most important person in the world, and he has to follow her around and protect her while being his usual grumpy self. Or it could be a fanfic set in an alternate universe where Sakura is a ninja assassin like Hidan, and they compete to see who can complete the most difficult assassination missions.
One idea could be the chibi versions of Akatsuki members getting into comical misadventures while trying to complete a simple mission. For example, they might mistake a cat for a powerful summon and end up chasing it all over the village. Another plot could involve them having a chibi-only Akatsuki meeting where they argue over who gets the last piece of dango. Or perhaps a chibi Akatsuki member accidentally uses a powerful jutsu in a wrong way and causes chaos in their hideout.
One plot idea could be that the reader is a healer who is forced to tend to Hidan's wounds after a battle. At first, Hidan is distrustful and rude, but as the reader continues to patch him up, he starts to see the value in their skills and a friendship begins to form. They then embark on a journey to find a rare herb that can cure a deadly disease affecting the reader's village.
First, you should decide on the basic plot. Are you going for a comical story, a more heartwarming one, or something else? For example, if it's comical, you can start with a scene where chibi Hidan wakes up in the Akatsuki hideout and everything is too big for him. Then, introduce his character traits in a fun way, like how he's still obsessed with his immortality beliefs even in his tiny form.
How about a Hidan crossover with the DC Universe? He could end up in Gotham City and be a new kind of villain that Batman has to deal with. His immortality would make him a very difficult opponent for the Dark Knight, and his disregard for life would put him at odds with Batman's moral code.
One interesting plot could be that chibi Naruto and chibi Sasuke get lost in a mysterious forest together. They have to work as a team to find their way out, which is a big challenge since they are so young. Along the way, they discover a strange creature that seems friendly at first but then turns out to be a bit of a trickster. Another plot could be a day - in - the - life kind of story where they are at the ninja academy and get into all sorts of silly mischief, like pranking their teachers or competing in a very unorthodox mini - ninja competition among the students.
One plot idea could be that chibi Sasuke, with his precocious nature, looks up to older Naruto who has become a respected ninja in the village. Sasuke could be constantly trying to prove himself to Naruto, leading to various comical and heartwarming adventures as Naruto mentors him in a way.
One interesting plot idea could be a chibi adventure where Sasuke and Sakura are on a mission to find a rare flower for a sick friend in the village. Along the way, they face little challenges like crossing a small stream filled with slippery rocks. Another could be a day in the life of their chibi versions at the ninja academy, with Sasuke trying to show off his skills and Sakura getting exasperated with him in a cute, chibi way. Maybe they also participate in a chibi - sized ninja tournament together and have to learn to work as a team.
Perhaps in this fanfiction, the magical world would be seen from a different perspective. Hidan's influence could lead Harry to question the traditional ways of Hogwarts. He might learn some unorthodox combat or survival skills, which would be really cool to read about. It could also change his relationships with his friends. For example, Ron might be a bit more wary of Harry because of his new, more radical ways.
A fanfiction could explore a scenario where Hidan is injured and Itachi has to take care of him. Itachi, being the more composed one, tries to keep Hidan in check while also learning about Hidan's unique immortality. This could lead to some interesting conversations between them about life, death, and their roles in their respective organizations.