Aang might go into a deep state of depression. He has always been an emotional character, and having his heart broken by Katara, someone he loves deeply, could send him into a downward spiral. He might isolate himself from his friends and stop practicing his bending for a while.
He could also become angry. Aang is not just a passive character. His heartbreak might turn into rage towards Katara or even towards the situation in general. He might lash out at those around him, feeling that they don't understand his pain.
Katara could be heartbroken. She might initially be in denial, not believing that Aang has actually left. Then she could become angry, feeling betrayed by Aang's sudden departure.
Perhaps Katara falls in love with someone else. In a fanfiction scenario, she might meet a new character who she feels a stronger connection with. This new relationship could cause her to break things off with Aang, shattering his heart in the process.
In some cases, the anger could be a catalyst for a more romantic development. Aang expressing his strong emotions might make Katara realize the depth of his feelings for her. Or it could be the other way around, Katara's reaction to his anger could make Aang see her in a new light, leading to a shift in their relationship dynamic towards a more romantic one.
Their relationship could deepen as they share in the joys and sorrows of rebuilding the world. They've been through a lot during the war, and now they can truly rely on each other. They might become even closer friends at first, with a mutual respect for each other's abilities growing stronger.
Their relationship often develops through shared adventures. They face many challenges together, which makes them rely on each other more and more, leading to deeper feelings.
The Fire Nation, which has now become more of an ally, would also see this as a positive thing. Zuko, being Aang's friend, would be happy for them. He would see it as a sign of peace and unity among the different nations. The Fire Nation people might send some precious gifts as a sign of their respect for the union, as they know how important the Avatar and Katara are to the new world order.
Toph would be blunt about it. She might tell both Aang and Katara that they're being stupid if she thinks the break - up is over something silly. But if it's a more serious issue, she'd support them in her own way. She might offer a place for Katara to stay if she needs to get away from Aang, or she might give Aang some tough - love advice on how to handle the situation.
In some fanfictions, Katara might be depicted as hurting Aang. This could be due to misunderstandings or different plot developments created by fans. However, it's important to note that these are often creative interpretations that may deviate from the original show's character dynamics.
In modern fanfiction, their relationship might develop slowly as they navigate modern - day life. For instance, they could start as friends who meet at a coffee shop regularly. As they share their dreams and fears, they realize they have deeper feelings for each other.
Sokka would probably be overprotective. He's always been protective of Katara, and now with her being pregnant, he would be constantly worried about her safety and the well - being of the baby. He might offer all kinds of advice, some of which might be a bit silly but well - intentioned.