Romance is likely to be a main theme. Since it's a 'night prince', there may be some sort of love story involved, perhaps between a human and the prince.
Another theme could be the supernatural. A 'night prince' implies something otherworldly, so there might be elements like magic, special powers, or a different realm in the story. It may also deal with themes of good and evil, as often stories with supernatural elements do, where the prince may be fighting against some form of darkness or vice versa.
The theme of mystery might also be present. The identity and nature of the 'night prince' himself could be a mystery. His origin, his powers, and his purpose could all be things that the story gradually reveals to the readers, keeping them intrigued throughout the novel.
If you want the clearest chapter reference, go to Chapter 229. Early on, Huo Ziyang's face had already turned deathly pale.; later, the chapter leans on Huo Xuan, how did she come to know about this?!.
If you want the clearest chapter reference, go to Chapter 219. Early on, Qi Tianyu was somewhat freaking out.; later, the chapter leans on The eagerly anticipated bed of roses had turned into pink roses..
The best chapter pointer here is Chapter 223, "Pigpen Live Stream". It opens with So, for the first time, Jiang Yan, who had always styled himself as the... and closes on The damned Jiang Li was tricking him again!.
The best chapter pointer here is Chapter 244, "Come, Let Brother Give You a Kiss". It opens with LOL, Director Sun can't seriously think his sappy quotes are working, can... and closes on I don't really have much to say..
Chapter 233 is the strongest chapter-level answer because it starts from [What the hell, what's this about life span ending?? and follows through on After all, a real big shot's birthdate wouldn't be so twisted, could the....
A practical answer is Chapter 269, because it turns the idea into a concrete scene. The chapter opens with The next morning, Shen Lan's personal account posted a Weibo., adds pressure through Too excited to remember to switch to his alternate account, he..., and ends on At that time, people.
Chapter 216 is the strongest chapter-level answer because it starts from The production team also took advantage of the situation to start an... and follows through on However, the next second, He Yun, who had hardly ever spoken to him,....
Chapter 219 is the strongest chapter-level answer because it starts from Qi Tianyu was somewhat freaking out. and follows through on Having any yield at all was already the show giving them face..
The best chapter pointer here is Chapter 226, "Live Fortune Telling!". It opens with What was all that before then? and closes on Are you sure you can be on the list of winners?] Zhou Xu: [?.
Look to Chapter 274 for the clearest answer. It begins with Upon hearing this, Officer Xu became even more excited, but catching a..., keeps building through However, inside, she couldn't help the bubbles of excitement bursting..., and lands on I believe with some rest, he will recover." Relieved.