Love in the Moonlight (Hangul: 구르미 그린 달빛; RR: Gureumi Geurin Dalbit; lit. Moonlight Drawn by Clouds) is a South Korean television series starring Park Bo-gum and Kim Yoo-jung. It is a coming-of-age story and youth romance set during 19th-century Joseon Dynasty. The series is based on the web novel Moonlight Drawn by Clouds, which was first serialized on Naver in 2013 and consequently published as a five-part series of books in 2015. It airs every Mondays and Tuesdays at 22:00 (KST) on KBS2, starting August 22, 2016.
It was Web Novel first but it got so popular that published as few books( Total 5 books). The Web novel & books have a lot of illustrations that die for. The story line is little bit different as well. I hope you can read Korean. Moonlight Drawn By Clouds: Episode 3
As Prince Yeong is dressed in his dragon robes, faithful Eunuch Jang clucks on about how kids these days are so hopeless, turning in blank test papers without even trying. He’s referring to Ra-on’s blank entry in the last of her eunuch exams, not knowing that she’s desperate to fail and get the hell out of here.
Bodyguard Byung-yeon suddenly interrupts them to say that the prince needs to go somewhere, right this instant.
In the dungeon, Princess Myeongeun is seconds away from slicing Ra-on’s throat for her imposter love letters, but just as she raises the sword to strike, Yeong’s voice commands, “Stop!” Everyone freezes at the announcement of the crown prince, and Ra-on cranes her neck to get a look at him. But his face is obscured by light, and the guard orders Ra-on to lower her head in respect. Damnit, she doesn’t get to see his face at all.

Yeong says that the princess will hurt herself by holding the sword that way, and takes it out of her hands. Then he demands in a booming voice to drag Ra-on to the Euigeumbu, and even Princess Myeongeun says fearfully that nine out of ten people die when they’re sent there.
Yeong plans to get to the bottom of this crime and even involve the king, and the princess suddenly balks at the idea of having the entire palace know about her embarrassment. She begs for Yeong to withdraw his order, and the cheeky glint reappears in his eye for a fleeting second before he turns concerned eyes on his sister. He tells Myeongeun that it won’t make her feel better to kill this eunuch, and that she’s not capable of taking a life.
As Yeong leads his sister away, Ra-on cries out on her hands and knees that she’s genuinely sorry for ghostwriting those love letters. She says that it never occurred to her how much that could hurt someone, and says through tears that she’s deeply sorry for what she’s done.

Byung-yeon asks the prince why he doesn’t reveal his identity to Ra-on when (s)he’s bound to find out, and Yeong just answers back that in the process he’ll gain one more subject on his side. He raises an eyebrow at the disapproving court ladies who pass by, and admits that he’d be sad if Ra-on looked at him with those eyes. Aw.
Both Ra-on and Do Ki are glassy-eyed from their near-death experience as the entire class gathers for their final exam results. Ra-on slaps her face to attention and brightens at the thought that this nightmare is almost over…
Hong Si-wan, Seoul