Yexian was based off of Esen Taishi. You should search up how he looks in ancient paintings ( ͡° ͜ʖ ͡°)
I watch kdramas too and I don't think they look korean. Maybe you just don't know enough about chinese culture. Ming and Joseon existed during the same era and were influenced by Yuan, so of course they would look similar. All of these styles are native to china except for certain things like the square collar (korean), tieli robe (mongol), etc. When the Joseon characters showed up I could immediately tell they were korean because of their hat. Also when I mentioned Esen I was trying to tell you that he doesn't look hot in real life, lol.
So is Ying Kong Shi now a bird and flies against that rock, dies and Ka Suo wakes up??? Really???
It's good. Written in first person perspective, it was very detailed in describing the four main characters' emotions, to the point that I could feel their deep despair. It had enough content to describe the of cause and effect of the tragedies and explain the characters' extreme behaviors. All the suspense, prophecy, and symbols have clear explanations. In contrast, the drama felt.... shallow. As for the plot, the differences are huge. The book is quite short, so the drama added a lot more side characters and plot, which I find too distracting because the bromance should be the main focus. I'd say the biggest difference is that the book is focused on defeating evil Yingkongshi instead of the fire tribe, and focused on bromance instead of friendship. The ending was also completely different, no happy ending. It left me in deep thought.
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https://hawonderful.wordpress.com/2013/05/16/bu-bu-jing-xin-chapter-1-part-1-by-tong-hua-translated-by-hawonderful/