There are some points I need to make them clear as to proceed the story so please read it thoroughly.
Firstly this is for everyone who is saying that it would've been better to complain to the police but we shouldn't forget bout certain factors in the story which are as follows:
When everything happened with Taeji and Taehyung got to know bout it he thought to handle it on his own the reason being that his marriage was already fixed with Jungkook and not to forget that was the first time his parents asked him to do something.
The other reason is as it's already shown he is hella rich so the world follows Kim's that's why getting such a matter out in public would've affected his reputation, his family's reputation..this could've affected their business as well.
There would've been various rumors as well which could stress his sister (Taeji) more or could affect her health as he saw her in that disheaveled look (According to Taehyung's perspective as a brother)..he also thought that if media got to know it his sister's life wouldn't be same either as it was such a sensitive topic though it was all false but he didn't know at that time.
Other reason is POWER as in the story he is shown as the most powerful person who no one dared to fuck with..he loves his family so much so that's why according to his perspective he thought to give better punishment to the culprit on his own.
Now the next part is how Jungkook got stronger in six months or what being stronger means!?
Here's the answer to it as well
As it's already shown how Jungkook was treated back in his home..he never really got that family love from his parents or brother that's why he was hungry for love. So when he first met Taehyung he fell for him..he already accepted Taehyung as his.. that's why he let Taehyung do whatever he wanted. Not to forget as shown in the chapter where Taehyung punished him in the worst way after being accused by Taeji of rape he was still asking Taehyung to love and care for him and not to forget that mirror breaking part so you all should know how fucked his mind was that time.
That's why when he got the genuine and real love from Mrs. Kim and Mr. Kim he opened up and like parents should guide their child they did the same to him..he also got Jihoon as his best friend which he never had. So in all these six months he was fully surrounded with people who love and care for him. He healed mentally and emotionally first..then in the US he also got physically strong by learning new skills and martial arts as some of you don't know learning self defence makes a person stronger physically and mentally both as it give a sense of security and safety to them which they were finding in someone else but finally got it in their self only.
Because of Taeji and his strict father he didn't communicate with many people but he did that freely in US which made him confident and social. After talking to so many people and getting fit he realises that he is not an ugly person either that also made him more confident in himself as it's very common when we look pretty we feel pretty.
So this is what I mean from being stronger.
Mr. and Mrs. Kim are in fault or not that you all will know in next chapter.
I'll post the new chapter tomorrow..I couldn't post it today as so many people were not able to understand it or were misunderstanding the theme.. that's why I couldn't write the chapter today in this much doubts and clarifications..will surely post it tomorrow.
Thank you for liking the story guys.