It might be related to Naruto's training. In some fanfictions, sealing Naruto's chakra could be a part of a unique training method. By restricting his access to his chakra, it forces Naruto to develop other skills and better understand the nature of chakra control, kind of like how in the original series he had to learn to use the Nine - Tails' chakra in a controlled way.
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.
Perhaps it's a plot device to introduce a new power or ability. With his chakra sealed, Naruto has to find a new way to be strong. This could lead to him discovering a hidden power within himself that was overshadowed by his original chakra, or it could even be a way for him to bond with other characters in the fanfiction who help him in this new power - seeking journey.
The best chapter pointer here is Chapter 86, "If you don't welcome me, why should I stay?". It opens with After over an hour of fuss, it was finally time to eat. and closes on But then her expression became resolute and arrogant..
Chapter 94 is the strongest chapter-level answer because it starts from Jiang Li really has some skills, being able to figure that out." "Can the... and follows through on Brother is going to dress you up; look how pretty this outfit is."....
A practical answer is Chapter 62, because it turns the idea into a concrete scene. The chapter opens with Sitting on the edge of her bed, she pondered for a while before lifting..., adds pressure through And it had been seven days since his last dose., and ends on Jiang Li reached in, pulled out a.
Look to Chapter 60 for the clearest answer. It begins with What's with Jiang Yan, treating his own sister Jiang Li like this?" "He..., keeps building through When Jiang Li found a place to live, she didn't bother with him either,..., and lands on And in traditional characters?" "What else?.
A practical answer is Chapter 80, because it turns the idea into a concrete scene. The chapter opens with Jiang Yan and Wen Jiaojiao, one so smug he was almost ascending to the..., adds pressure through There's abalone, eels, crabs, isn't that tycoon enough?" "Hang on." Shu..., and ends on.
Look to Chapter 99 for the clearest answer. It begins with Seeing the man approach, one of the individuals with a long scar across..., keeps building through How is it, have those people outside left?" "They're gone." The man spat..., and lands on Just as she was considering whether to practice a.
A practical answer is Chapter 72, because it turns the idea into a concrete scene. The chapter opens with Jiang Yan was still griping when suddenly a fair hand reached out beside..., adds pressure through [HAHAHAHAHAHA, this is the first time I've seen Director Sun speechless.]..., and ends on.
Chapter 73 is the strongest chapter-level answer because it starts from Director Sun, tongue-tied, finally managed to squeeze out a sentence,... and follows through on Despite Wen Jiaojiao's fiery temper, there were still many who were drawn....
If you want the clearest chapter reference, go to Chapter 85. Early on, Facing everyone's skepticism and curiosity, Jiang Li explained fluently:...; later, the chapter leans on The tomatoes are grown by them, and the eggs are also from their....
The best chapter pointer here is Chapter 107, "Are You Really Going to Participate in That Variety Show?". It opens with On the plane, when He Yun had taken off his mask and greeted her... and closes on Although Su Yinwan's recent change in temperament had been hard for her to....