They could see a future where Hawk Moth has turned all of Paris against them. In response, they might start working on their public image in the present, doing more heroic deeds that are visible to the public and trying to win the people's trust back before it's too late.
One plot idea could be that Ladybug and Chat Noir see a future where Paris is in ruins because they failed to stop Hawk Moth. This would give them the motivation to find a new strategy in the present, like seeking out new allies or uncovering a hidden power of their Miraculouses.
One idea could be that Hawk Moth finally manages to get hold of both the Ladybug and Cat Miraculouses and the heroes have to find a new way to fight him, perhaps by teaming up with some of the minor characters who develop new powers. Another could be that Ladybug and Cat Noir have to travel to the future to stop an even greater threat that is related to Hawk Moth's actions in their present time.
In a 'Watching the Future' Miraculous Ladybug fanfiction, Ladybug and Chat Noir might see their future selves facing a super - powerful villain. They could then start training harder in the present to be better prepared.
Well, it could be about Ladybug and Chat Noir finally revealing their identities to each other and having to deal with the consequences. Maybe they face a new, more powerful villain that is a threat to all of Paris and they have to use their combined powers in new ways.
One idea could be a story where the Peacock Miraculous has a unique malfunction that causes it to create unexpected akumas. For example, instead of creating the usual villains, it creates akumas that have the power to spread positive emotions but in a chaotic way that still disrupts Paris. Another idea is a fanfiction where the holder of the Peacock Miraculous has to team up with Ladybug and Chat Noir to fight against an ancient evil that is specifically drawn to the power of the Peacock. This could involve exploring the history of the Miraculous and its connection to this new threat.
One idea could be Multimouse having to team up with an unexpected ally, like a villain who has a change of heart for a short time. Another could be Multimouse getting lost in an alternate dimension and having to find her way back while facing new challenges.
One idea could be Ladybug and Chat Noir having a heart - to - heart conversation in bed after a particularly tough battle. They could share their fears and insecurities that they usually hide behind their superhero personas.
One idea could be a story where the child of Ladybug and Chat Noir discovers their parents' secret identities by accident. Maybe they find a hidden Miraculous box in the attic and start to figure out what it means.
For a Miraculous Ladybug class fanfiction, a plot about a cursed object in the classroom could be interesting. The object spreads negative energy, causing the students to fight and argue more. Ladybug and Chat Noir suspect that it's an akuma - related thing, but they can't find the akuma. As they investigate, they discover that it's actually an ancient cursed item that was accidentally brought into the class. They have to find a way to break the curse without revealing their identities, and also deal with the fact that their classmates' relationships are falling apart because of the curse.
Maybe there's a werewolf akuma. Hawkmoth takes advantage of an already existing werewolf in the city and akumatizes it. This werewolf - akuma has enhanced powers and is causing chaos. Ladybug and Chat Noir must figure out how to defeat it. They might need to discover the true identity of the werewolf to break the akuma's hold. It could be a person who was bitten recently and is struggling to control their new form.
Another plot could be that a crime wave hits Paris, and all the evidence points to Chat Noir as the perpetrator. Ladybug is torn between believing in her partner and the mounting evidence against him. She has to dig deeper into the case to find the real criminal who is framing Chat Noir and clear his name.