Maybe he has his own principles. In some fanfics, Harry might have a different view of SHIELD's methods or goals. He could be more of a lone wolf type and doesn't want to be part of a large organization like SHIELD.
He could be seen as an enemy. SHIELD might not take kindly to someone with Harry's potential abilities refusing to join them, and they could view him as a threat. This could lead to them trying to keep an eye on him or even take action against him if they think he's up to no good.
It means that Harry has a negative attitude towards fanfic. Fanfic is fan - written fiction based on existing works. Harry might refuse it because he values the integrity of the original work. He could also be worried about legal issues associated with fanfic, such as copyright infringement. Additionally, he may not like the idea of others taking creative liberties with something he is associated with.
It could be that he has some personal traumas related to fighting. For example, he might have seen the negative consequences of fighting in the past, such as the loss of loved ones or destruction of places he cares about, so he refuses to engage in it. In addition, he may also be influenced by certain moral or ethical beliefs within the context of the fanfic's world, which lead him to oppose fighting.
One possible reason could be his loyalty to his own village and friends in the Naruto world. He has strong bonds there and wouldn't easily abandon them to join someone in a different fictional context like Rias. Another reason might be the difference in values. Naruto values hard work, friendship, and the will of fire, while Rias's group may have different goals and values that Naruto doesn't align with.
One possibility is that Harry stands up against an unfair detention. Maybe he has evidence that he was wrongly accused of something, like when Snape tries to give him detention unjustly. So he refuses and decides to take his case to Dumbledore, who then investigates and clears Harry's name.
He could be seeking revenge. After being betrayed, Percy might see Shield as a means to get back at those who wronged him. By joining Shield, he may think he can gain the power and resources needed for revenge.
One great fem Harry works for SHIELD fanfic is 'Agent Potter'. It has an interesting take on how a female Harry would adapt to the high - tech and often secretive world of SHIELD. The story does a wonderful job of showing her using her Gryffindor - like courage in new and dangerous situations.
Well, perhaps Harry might refuse the marriage contract because he has his own dreams and goals that don't align with the traditional expectations of the contract. For example, he may want to focus on his magical studies or his adventures without the constraints of a marriage. Maybe he has feelings for someone else who is not the person in the contract.
Hermione would probably be a bit worried at first. She's always been one to follow the rules, but she also supports Harry. So she might try to convince him to find a more diplomatic way to handle it. Ron, on the other hand, would be more on Harry's side right away. He'd say something like 'Good for you, Harry!' The teachers would be shocked. Snape would be furious and might try to give him an even harsher punishment, while McGonagall might be more understanding and listen to Harry's reasons.