I love this character a lot.

When he’s introduced in the novel, he’s 20 years old. We meet a much younger Shi Ying in the drama, as a crown prince. He should be about 13 years old or younger. As expected of a crown prince, he’s mature from a very young age. His relationship with his father, the emperor, adds to his sensibility.
We meet Shi Ying again in Jiuyi Mountain. It’s been 5 years. He lives in seclusion in the mountain and does not concern himself with worldly affairs (aside from his mother).

Actor Xiao Zhan does a good job in humanizing Shi Ying. Based on the novel, Shi Ying can come out as cold and almost unfeeling but the drama’s Shi Ying is a gentle monster. He’s got a big heart and takes after his mother. Xiao Zhan is also good at nailing the micro expressions. You’ll know what I’m talking about in episodes 5.
What makes a project a success is the actor embodying the character. Xiao Zhan does this with all his characters. When I’m watching the Longest Promise, I don’t see Xiao Zhan, I see Shi Ying.
If I talk anymore then I’ll be spoiling it for those who haven’t watched the drama so please go watch and don’t be dissuaded by negative reviews. That’s just a basic lack of understanding on their part especially where Xiao Zhan is involved.
Happy watching!