In some fanfictions, it might be through a sudden reveal or a series of clues that lead him to the truth.
Maybe through a secret clue or a special event that reveals her identity.
Sometimes, it could be through a magical reveal or a series of clues that he pieces together.
Yes, in some fanfics Adrien does know. It depends on the creativity of the author.
It might be that a trusted ally shares some vital information with Adrien, allowing him to piece together the mystery of Hawkmoth's identity.
One idea could be that Adrien initially feels shocked but also a sense of relief. He might have always had a feeling that Marinette was special, and now it all makes sense. So he starts to view her in a whole new light, with more respect and admiration for her dual identity.
It's possible that a trusted ally shares vital information with Adrien, enabling him to unmask Hawkmoth. Or, maybe he catches Hawkmoth in the act during a critical moment.
Maybe through some clues and his own detective work. He could have pieced things together after observing certain patterns or actions.
Their relationship would probably become more complex. Adrien might feel a new sense of closeness to Marinette.
Well, it could be a bit rocky at first. Adrien might be in disbelief and not know how to act around Marinette. But as time goes on, he could start to see all the times Marinette has shown the same qualities as Ladybug, like her courage and kindness. This realization would slowly bring them closer. For example, he might remember all the times Marinette has stood up to bullies at school, just like Ladybug does against villains. Eventually, they would have a deeper, more meaningful relationship.
Some fanfictions might handle it by exploring Adrien's inner turmoil in great detail. They could show his gradual descent into hopelessness through his thoughts and interactions. For instance, by depicting his lonely nights and how he contemplates his worth.