In some fanfictions, Adrien's reaction could be complex. He may try to reason with his father, believing that there is still some good in him. He could struggle between his loyalty to his family and his sense of justice as Chat Noir. This internal conflict often makes for a very interesting plot point in the fanfictions.
He might be shocked at first. In many fanfictions, Adrien would feel a mix of disbelief, anger, and sadness. He has always known his father as a strict but loving parent, and finding out he's Hawk Moth, a supervillain, would completely shatter his view of him.
Well, initially, Adrien would likely be in denial. He loves his father and has seen no signs of him being Hawk Moth in his normal life. But as the truth sinks in, he would have to face the reality. Depending on the nature of the fanfiction, he might either confront his father immediately or try to gather more evidence first. He would also have to deal with the fact that his own family has been causing so much chaos in Paris. This discovery could change his whole dynamic with his friends and his role as a superhero as well.
If you want the clearest chapter reference, go to Chapter 1. Early on, Jiang Li, I'm warning you, don't set your sights on Yinwan anymore, or...; later, the chapter leans on Following a bout of tinnitus, she struggled to open her eyes and finally....
Chapter 939, "When Did the River Moon First Illuminate People? [Extra · River Moon Chapter]", is the clearest early answer because it turns Seeing Jiang Yan's situation into a concrete plot event. It opens with Using food to win over Shang Shuyue really works.
Chapter 682, "Too Conspicuous to Keep Around", is the clearest early answer because it turns Ye Chu's situation into a concrete plot event.
Chapter 924, "Competing to Auction Themselves", is the clearest early answer because it turns Jing University's situation into a concrete plot event. The chapter turns that into something concrete by moving from Not only did the netizens feel like they were on a roller coaster,...
Chapter 853, "The Bracelet Worn by the Empress?!", is the clearest early answer because it turns Rong Sheng's situation into a concrete plot event. Early on, Jiang Li carefully examined the branches and leaves for a while.. By the end, After all, it's just an object;
Chapter 781, "Master, accept my bow!", is the clearest early answer because it turns Chang Rong's situation into a concrete plot event. It opens with Not only were the criminals curious, but so were the others. and closes on I really was chosen, I knew there was something wrong…" The audience....
A practical answer is Chapter 24, because it turns the idea into a concrete scene. The chapter opens with Not only that, even the non-mainstream photos she had previously posted on..., adds pressure through Just because of his arrival, both were severely affected by public..., and ends on Shi Xu.
Chapter 769, "Su Yinwan Gets into Trouble!", is the clearest early answer because it turns Jiang Li's situation into a concrete plot event. The chapter turns that into something concrete by moving from The Jiang Family's banquet caused quite a buzz online.