Often, Gwaine reacts with acceptance. He's not the type to shun Merlin just because of his magic. Instead, he'll likely embrace it as part of who Merlin is. He could say something like 'Merlin, your magic doesn't change a thing between us. You're still my friend.'
In some fanfictions, Gwaine might be initially shocked. But given his loyalty to Merlin, he would probably keep the secret. He could also become an ally in Merlin's magical endeavors, using his fighting skills to protect Merlin when his magic is revealed to more dangerous foes.
Well, Arthur's reaction can be complex. At first, he might be angry because Merlin has kept this big secret from him. However, as he thinks about all the times Merlin has saved his life with magic, he begins to see that magic isn't all bad. He may feel betrayed, but also grateful in a way.
He could be very surprised at first. Maybe he's just out on a normal day in the forest and suddenly comes across a baby. His immediate reaction might be to look around for any sign of the baby's parents.
In some versions of this type of fanfiction, Arthur's reaction is complex. He might be stunned into silence when he first finds out. His mind would be racing with thoughts about all the times Merlin has used his magic to save him or Camelot without his knowledge. After the shock subsides, he may have a heart - to - heart with Merlin. They would talk about the implications of the secret, and Arthur would likely start to view Merlin in a whole new light, as not just his servant but as a powerful ally with a great burden.
She could be shocked at first. After all, Merlin has been hiding his magic for so long. Maybe she feels a sense of betrayal initially, but then she might see an opportunity to have an ally in the world of magic.
He might be shocked. Fanfiction can often be quite different from the original source material, and the nogitsune concept is already pretty out - there. So the shock value could be high.
In many fanfictions, Naruto's reaction is a mix of shock and determination. The shock comes from finally learning about his clan, and the determination is to uphold the Uzumaki name. He could start wearing something that represents the Uzumaki clan, like a symbol on his clothing. He also may become more protective of the Uzumaki secrets and legacies he discovers.
Steve is usually shocked and conflicted. He might question a lot of things and have mixed emotions.
He would be very angry. Naruto is not one to take betrayal lightly.
In some fanfictions, Vegeta is initially shocked. He might stand there in silence for a moment, his eyes wide. Then he could feel a strange mix of emotions, like pride and fear. He's proud to be having a child with Bulma but also fears for the safety of his family given his dangerous past and the many enemies he has.