One possible plot idea could be that Ladybug and Chat Noir are on a beach vacation. They are trying to enjoy a normal day at the beach in their swimsuits when an akuma shows up. The akuma targets a beach volleyball tournament, and Ladybug and Chat Noir have to transform and fight while still in their swimwear, which could add some comical and interesting challenges like trying not to lose their masks in the water or dealing with sand getting in their suits during the battle.
Maybe there could be a story where Marinette (Ladybug) designs special swimsuits for herself and her friends that have some kind of hidden superpower. For example, the swimsuits could allow them to swim super fast or be able to breathe underwater. But then Hawkmoth tries to steal the design to use for his own evil purposes, so Ladybug has to protect her designs and her friends while in her swimsuit-themed hero form.
Another plot could involve a new villain who has the power to make swimsuits come to life and attack people. Ladybug and Chat Noir find themselves in a beach town full of chaos as people run from the attacking swimsuits. They have to figure out the villain's identity and weakness while also looking stylish in their own swimsuits. Their Miraculous powers might interact in strange ways with the water and beach environment, like Ladybug's yoyo might turn into a beach ball - like weapon when near the water.
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.
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 possible plot for a Miraculous Ladybug beach fanfiction is that Hawkmoth sends an akuma to the beach during a big surfing competition. Chat Noir is there to compete, and Ladybug has to show up and they end up having to fight the akuma while also trying to protect the civilians at the beach. They could also have some cute beach - themed banter in between the fight scenes.
One possible plot could be that the peacock miraculous has a new holder. This new holder might be a bit of an anti - hero at first. They could use the peacock's powers to create sentimonsters for their own gain, like stealing valuable items. But as the story progresses, they start to see the harm they're causing and slowly turn towards the side of good, joining Ladybug and Chat Noir in their fight against Hawk Moth.
One idea could be that Trixx gets lost in the human world and has to find its way back to its Miraculous holder. Along the way, it teams up with a human who has no idea about the Miraculous but is kind-hearted and helps Trixx avoid the villains who are also after it for their own devious plans.
A new villain could have a weapon that specifically targets Ladybug's powers. When she tries to use her yo - yo or her powers of creation, it backfires and causes her harm. This would force her to rely on her wits and Chat Noir more than ever. They would need to find a way to neutralize the weapon and heal Ladybug.
One idea could be a story where Mylene uses her acting skills to help Ladybug and Chat Noir in a different way. Maybe she pretends to be a decoy to draw out an akumatized villain. It could show her courage and her ability to think on her feet.
Perhaps it's a story where Roxas is transported into the Miraculous Ladybug universe and teams up with Marinette and Adrien. He could bring his unique skills from his own world to help them fight against Hawk Moth. There could be a lot of character development as he learns about the power of the Miraculouses and the importance of friendship in this new world. For example, he might initially struggle to understand the concept of the Miraculous transformations but gradually grow to master it with the help of his new friends.
One idea could be a fanfiction where Marinette discovers that her Ladybug wings have a special power she didn't know about. For example, they can create a shield not just for her but for the whole city. This could lead to a new adventure as she has to learn to control this power.
One possible plot could be that Jagged Stone discovers the true identities of Ladybug and Cat Noir. Maybe he gets involved in one of their battles accidentally and then becomes determined to help them keep their secret identities safe while also using his fame to distract Hawkmoth.