Naruto would likely be extremely confused at first. He has always idolized his father, and to have Minato do such a thing would shatter his perception. He'd probably try to talk to Minato, ask him why he's doing it.
At first, Naruto might be in disbelief. But as the reality sinks in, he would be angry. He'd feel betrayed by his own father. He would then try to break the seal on his chakra. Naruto is a fighter, and he wouldn't just accept this situation passively. He might look for allies, like his friends or other ninja who could help him understand what's going on and how to reverse the seal.
Perhaps Minato has been corrupted by power. In the fanfiction world, he might have come across some source of power that has twisted his mind. By sealing Naruto's chakra, he could be trying to take that power for himself. It could also be related to some prophecy that he misinterprets. He thinks sealing Naruto's chakra is the key to saving the world, but in reality, it's the opposite.
It could make his friends more protective. Since Naruto is in a weakened state without his full chakra, his friends might be more concerned about him and try to keep him out of dangerous situations.
One reason could be for protection. Maybe in the fanfiction, there are powerful enemies targeting Naruto's chakra specifically. Minato, as his father, seals it away to keep Naruto safe from those who would misuse his power.
Minato would likely be extremely shocked. Naruto is his son, and the idea of Naruto attacking him would be completely unexpected. He would probably try to talk to Naruto first, to find out what is wrong and why he is being attacked.
They would be shocked at first. Minato would be filled with pride and joy seeing his son all grown up. Kakashi would respect Naruto's strength. Obito might be a bit envious of Naruto's popularity but also admire his spirit. Rin would be very friendly towards Naruto.
Sakura would be extremely worried. She would probably try to gather the other members of Team 7, like Sasuke and Kakashi, to go after them. Sasuke might be a bit more hesitant at first, but his loyalty to Naruto would eventually make him join the search. Kakashi, on the other hand, would be more strategic. He would try to figure out Minato's motives first and then plan the rescue mission accordingly.
They would be empathetic. Minato, as Naruto's father, would especially feel a deep sense of pain seeing his son struggle. He would want to reach out and comfort Naruto during his lonely times when the village shunned him because of the Nine - Tails.
Sasuke would be devastated. He and Naruto had a complex relationship, and despite their differences, they were like brothers. His reaction might be to isolate himself at first, blaming himself for not being there to protect Naruto. Sakura would be heartbroken. She had deep feelings for Naruto, and his death would be a huge blow. She might become more determined to protect the village in his memory. Kakashi would feel like he failed as a teacher. He always saw Naruto's potential and to lose him would be a great loss for him.
It can strengthen Naruto's relationship with his family on a spiritual level. Even though they are sealed within him, he might feel a closer bond to his parents. This could make him more confident in his identity as the son of Minato and Kushina.
When Team Minato meets Hokage Naruto in a fanfiction, their reactions would depend on their individual personalities. Minato would be overjoyed and would immediately start asking Naruto about his achievements and how he has led the village. Kakashi would be his usual calm self but would show his admiration through his words and actions. Obito, who has had a difficult journey, might initially be hesitant but then would be inspired by Naruto. Rin would be the most excited, perhaps jumping up and down and saying how wonderful it is that Naruto is the Hokage. This encounter could also lead to a deeper understanding between them all and a strengthening of the bonds between generations.