One reason could be that he's in a state of shock. Maybe he witnessed something really traumatic that made him unresponsive. For example, if he saw Ladybug in a life - threatening situation and couldn't do anything to help immediately, it might have sent him into a state of mental paralysis.
Another possibility is that he's under some sort of magical influence. In the Miraculous universe, there are many powerful magic - based villains. Perhaps one of them cast a spell on Adrien that made him unresponsive. This could be part of a larger plot to either take his Miraculous or to cause chaos in Paris.
It could also be related to his personal life. Maybe his father has done something extreme that has left him so shocked and unable to react. His father's controlling nature and the secrets in his family could potentially lead to situations where Adrien is just so overwhelmed that he becomes unresponsive.
Then, show his unresponsiveness through the reactions of other characters. If Ladybug tries to talk to him and he doesn't answer or even blink, it emphasizes his state. You can also use dialogue from the other characters to express their concern and confusion about Adrien's unresponsiveness.
It could also be due to a spell or an akuma's special ability. In the Miraculous universe, there are many powers that can immobilize characters. For example, if an akuma had the power to paralyze people, Adrien might have been caught in it. And since he's often in the middle of the action, he'd be a prime target. He might be motionless as his body is fighting off the effects of this external force, trying to break free from it so he can transform into Chat Noir and save the day.
In such a fanfiction, one possible reason could be the intense pressure he faces as a model and son. Constantly having to meet high expectations and having little personal freedom might drive him to despair. For example, his father's strict control over his life and his public image could make him feel trapped.
It could be related to his emotional state. Adrien has a lot of pressure on him, both as a model and as Chat Noir. The stress could have taken a toll on his health, causing him to collapse and be hospitalized. In the fanfiction, this could be the starting point for his friends, like Nino and Alya, to realize how much Adrien has been hiding and struggling, and they could come together to support him in a new way.
In the fanfic, it could be related to an emotional turmoil as well. Adrien has a lot of personal issues and secrets. If something really bad happened, like he found out some truth about his family that shocked him to the core, it might have made him distracted during a fight or a dangerous situation. This distraction could have led to him being in the wrong place at the wrong time and getting caught under the rubble when something like an explosion or building collapse occurred.
One possible reason could be that he got injured during a fight with an akumatized villain. In the Miraculous Ladybug universe, battles can be quite intense and Adrien, as Chat Noir, often puts himself in harm's way to protect Paris. Another reason might be some sort of illness that was magically induced, perhaps by a new villain with a different kind of power that targets the heroes in a non - traditional way. It could also be due to overexertion from using his Cat Miraculous too much without proper rest, which could lead to his body breaking down and him ending up in the hospital.
A great fanfiction idea could be that Adrien and Kagami are paired up for a school project. As they work on it, they start to realize that they have more in common than they thought. They could share their dreams and fears, and this new - found closeness might make Adrien question his feelings for Ladybug a bit more.
One possible story could be that Adrien gets akumatized because he feels constantly overshadowed by Ladybug. In this fanfiction, Hawkmoth might prey on his insecurities. As an akumatized form, Adrien could have enhanced physical abilities like super strength and speed. His akumatized look might be a dark version of his Chat Noir costume, with a more menacing appearance.
This fanfiction could be about many things related to an unresponsive Adrien in the Miraculous world. It might explore how his lack of response affects the other characters. For instance, if Adrien is unresponsive, it could make Marinette worried and she might try to find out what's wrong with him. The story could also be about how his unresponsiveness impacts the overall plot, like if he's unresponsive during a key moment in the fight against Hawkmoth, it could lead to some big changes in the story's direction. It could also be a character - study type of fanfiction, delving into Adrien's psyche when he's in this unresponsive state.
I really like 'Adrien's Discovery'. In this fanfiction, Adrien starts to notice Marinette in a new light. He begins to see all the little things she does for him and how selfless she is. It has some really heart - warming moments, like when Adrien defends Marinette from Chloe's mean remarks. It's a great read if you want to see more of Adrien realizing his feelings for Marinette.