I would like to start off that I only read up until chapter 5, so take this review with a grain of salt, and I will be mostly focusing on the main character/writing quality. The two main issues I noticed right off the bat is the fact that the character adapted to his circumstances extremely quickly. and the pacing of the story is over the roof, and to be quite fair. It makes no sense.
As a thirteen year old child people would expect them to be full of questions and have issues adapting, but instead we see him act like an adult and make rational and extremely unlike choices for a child. This makes no sense considering he just woke up and after an hour of him living his new life he already realized he is in the karate kid/cobra kai world.
His interaction with his father is also forceful, but that might be because of his strained relationship with his parents.
The pacing makes the unnatural adaptation of the child even worse, and adding another layer of doubt towards the novels progression. Since the pacing and character are so bad it is starting to affect the story development since chapter 5, and making the development less competent. basically we are rushing to build the house and forgot to reinforce the foundation, this will create plothole which leads to dissatisfaction.
World Background is 5*, cuz its a fanfiction held inside an already popular series.
Updates is 5*. lots of chapters and a really responsive author. good overall