In such a fanfic, Naruto would likely be deeply hurt. His trust in his friends being shattered could lead to him becoming more isolated. He might start to question his own worth and his ninja way. Maybe he would turn away from Konoha for a while to figure things out on his own.
He might overcome the betrayal by focusing on his own growth. By becoming stronger both physically and mentally, he could rise above the pain of betrayal. He could also look back on the good times with his former friends and use that as a motivation to move forward and prove himself.
Perhaps Danny's friends are lured by a powerful and evil ghost who offers them something they desire, like wealth or power. In exchange, they have to turn against Danny. They might start to sabotage Danny's ghost - fighting efforts, for example, by giving false information to his enemies. This would be a huge betrayal considering they were once his closest allies.
Danny would probably be extremely hurt. He might initially go into denial, not wanting to believe that his friends could do such a thing to him. He'd keep trying to reach out to them, hoping it was all a misunderstanding.
It could be that they were misled. For example, they might have been tricked into believing that Naruto was a threat to the village in the future. So, in an attempt to safeguard the village they love, they decided to 'betray' Naruto. This would add a lot of complexity to the story as Naruto discovers the truth later.
Sakura might be very worried. She's a medical ninja, so she would be concerned about the potential harm Naruto could be doing to himself. She'd probably try to stop him or at least monitor his experiments closely. Sasuke, on the other hand, might be more understanding in a way. He knows what it's like to push oneself for power, but he might also be a bit skeptical and warn Naruto about the risks.
Sasuke would likely understand Naruto's motives better than most. He himself has had his own reasons for leaving in the past. He might give Naruto some advice based on his own experiences, like how to survive in unknown lands. But at the same time, he would also be a bit envious of Naruto's new adventure.
Shikamaru, being the smart and observant one, would analyze the situation thoroughly. He would probably warn Naruto about the potential political pitfalls and how to navigate them. He might also offer some strategic advice on how to handle the relationship aspect, like how to communicate effectively with his new partner in the political marriage so that Naruto doesn't get caught up in unnecessary drama or power plays.
It's also possible that her adventure - team friends betray her. In a fictional world, if there are some high - stakes situations like a quest for a powerful artifact, they could betray her for their own gain, such as getting the artifact all for themselves.