Sun-woo brings Ah Ro a bouquet of chrysanthemums, recalling that she once used them to make a medicinal tea for him. She says softly that she's happy that he's her brother, which makes Sun-woo smile.
Ah Ro thinks back on her conversation with Sun-woo's first adoptive father Woo-reuk, where Woo-reuk had told her that Mak Mun always talked about her and dreamed of her, but now he's dead. Now Ah Ro tells Sun-woo that she knows he's not her brother. She drops the flowers and asks accusingly, "Who are you?"
Caught, Sun-woo doesn't deny the truth. He says that he's her brother's friend, and Ah Ro asks through angry tears what happened to her real brother. Sun-woo says that he died, and Ah Ro asks tearfully why her brother had to die while Sun-woo lived.
Sun-woo barely holds it together as he explains that Mak Mun died because he came back to help him (after they snuck into the capital), and was struck down. He says that he doesn't care whether Ah Ro believes he's her brother, because he intends to live as if it's the truth. Unable to bear it any longer, Ah Ro walks away from him.
Ji-dwi sees Ah Ro on her way out of the Hwarang school, and playfully jumps out to scare her before he realizes that she's sobbing. She keeps going so he follows her out, staying a short distance behind her as she walks aimlessly and cries.
She can't stop thinking of all the times Sun-woo pretended to be her real brother, and breaks down all over again. At the same time, Sun-woo beats a practice dummy savagely until he breaks his wooden sword and his hands bleed. It reminds him of when Ah Ro had bandaged his hand and asked him not to get hurt again, and he'd asked the same of her.
Ji-dwi covers his absence from the Hwarang school by making Pa Oh huddle in his bed with a "Do not disturb" sign next to him. Su-ho enters the room, balls up the sign, and asks the lump under the covers why nobody will tell him what happened the night they all went out over the wall. He says he feels like something weird happened, but he just can't remember.
Pa Oh starts to moan loudly, pretending to be sick. Su-ho smacks him and warns "Ji-dwi" not to mess up their performance in front of the queen regent at the Moon Festival, and finally leaves Pa Oh alone.
Ji-dwi eventually approaches Ah Ro and tries to give her silver back (that she gave him to pay off her debt). She ignores him, so he offers to either hug her or kill whoever made her cry like this. He threatens dire consequences to anyone who's bothering her, which is violent, but also kind of sweet.
Ah Ro looks up at him with big, tear-filled eyes, and says that she's the reason she's crying. Without revealing who she's talking about, she admits that she feels so much anger toward him, but she's also relieved, and she hates herself for being so torn.
She walks until after dark, and Ji-dwi stays right behind her. He vows that she can stop crying, because he'll make her his.
Eventually Ah Ro makes her way home, and she stares at her father as he works, silently asking, "Why didn't you tell me?" She wonders what his reason is for having Sun-woo pretend to be her brother, and what else Ji-gong is hiding from her.
Ji-dwi sneaks back over the Hwarang wall, and finds Sun-woo there waiting to ask about Ah Ro. Ji-dwi senses that Ah Ro's tears are because of Sun-woo, and asks how "someone" could hurt her so badly that she'd cry like that. Sun-woo just grabs him by the collar and desperately demands to know if Ah Ro is okay.
Sun-woo and Ah Ro both sit up late that night thinking about each other. Ji-dwi is also awake, and he tells Ah Ro's drawing of the birds in the tree (to represent the king and the queen dowager) that he pities her too, so he asks why she can't look at him the way he looks at her.
The queen regent is still fuming over her argument with Hwa-gong, angry that he plans to have the Hwarang perform in front of the people. She asks an advisor what he thinks of Hwa-gong, and he says that while he's the only person who can handle the Hwarang, he's also not someone to trust completely.
PRINCESS SOOKMYUNG causes a stir as she arrives in the city in a closed palanquin. She's been away recuperating from an illness, and is finally well enough to come home.
Sookmyung formally greets her mother, Queen Regent Jiso, at the palace, and coolly thanks her for her concern over her health. The queen regent steps close to hug her, but the princess's expression remains cold and distant.
The queen regent informs Hwa-gong that the princess has been highly trained in etiquette, music, and dance, and can be of help to him as he prepares the Hwarang for the Moon Festival performance. He jovially declines the offer, and the queen regent rounds on him and demands to know if Ji-dwi is really his nephew.
She tells Hwa-gong that although she let Ji-dwi into the Hwarang because of their agreement, he'd better not turn out to be a spy, and she asks for proof of his real identity. This worries Hwa-gong, as he knows nothing about the young man who calls himself Ji-dwi, other than that he wants to drag the queen regent down.
The queen regent tells Hwa-gong that if she decides to torture Ji-dwi, he'll confess the truth before he dies. Hwa-gong asks if she's making a bet with him, and tells her to do as she wants. He agrees to let Princes Sookmyung into the Hwarang school.
Ah Ro is still preoccupied as she brings Hwa-gong tea later that day, and he takes note of her distracted expression. She asks if Sun-woo will be a great Hwarang member, and if he's someone trustworthy. Hwa-gong doesn't answer, and Ah Ro takes the tray and leaves, dejected.
She grumbles to herself while she does laundry, and finds Ji-dwi lurking behind a hung sheet. He notices the disappointment in her eyes when she realizes he's not Sun-woo, and she tells him to leave her alone.
He yanks her close, and Ah Ro asks if he's planning to kiss her again. He says he could, and asks if she can really stand so close and not feel anything, when he's standing there inwardly screaming that he likes her.
When Ah Ro stays silent, Ji-dwi asks again if she really feels nothing. She looks him in the eye and asks if Sun-woo is okay. Well, that answers that question.
She moves aside to sit down, and Ji-dwi sits beside her and shields her eyes from the sun with his hand. He says that he's disappointed, but adds that at least they got a little closer.
Ah Ro looks past Ji-dwi, and sees Sun-woo watching them from a short distance away. When Ji-dwi also sees Sun-woo standing there, Sun-woo turns and walks away.
Hwa-gong greets Princess Sookmyung at the Hwarang gates and offers to show her around. She says curtly that she'd rather look around by herself, and Hwa-gong mutters that she's just like her mother.
The boys watch Sookmyung from a distance, and Han-sung is impressed by his first look at a real princess. Su-ho wonders why she's here, and Yeo-wool figures she came to the place where the best men in the capital are gathered, to find a husband.
Su-ho sneers that she looks nothing like her mother, and calls the princess's expression cold. Han-sung says confusedly that the queen regent seems much colder, ha.
Ji-dwi and Pa Oh look on as the princess continues around the grounds, and Ji-dwi wonders what Sookmyung thinks about the things their mother is up to.
Sun-woo goes to mope by the river, still troubled by Ah Ro's reaction to the truth that he's not her real brother. He sees the princess a short ways downriver and watches as she looks around to make sure she's alone before taking off her shoes to dangle her feet in the water.
A little while later, Sookmyung is half-dozing by the water, and she opens her eyes to see Sun-woo approaching. She reaches for her sword when he draws his practice sword, but he's not attacking her — instead, he swipes a snake off of the tree branch just above her head.
Sookmyung draws her sword to kill the snake, but Sun-woo knocks her sword aside. He gently flips the snake to safety, and Sookmyung levels her sword at his throat and asks why he didn't kill the venomous snake.
Sun-woo just knocks her sword aside again and asks why he should kill it when it's not the snake's fault it was born venomous. He leaves after telling Sookmyung to be more careful.
Back at the Hwarang school, Sun-woo silently takes a box of books from Ah Ro and carries it to the doctor's room. She follows him in and asks what he'll do if she can't keep pretending he's her brother. Sun-woo answers that he'll live as her brother, no matter what she does.
Ah Ro calls him a liar, reminding him that he said he remembered their childhood, her voice faltering. In response, Sun-woo begins repeating things about her that Mak Mun probably told him a thousand times — that his sister was burned by a brazier, that she cried, and that she was pretty.
Fighting back tears, Ah Ro asks Sun-woo his real name. After a long pause, he says that Sun-woo is his only name, because he never had a name before (Moo-myung means "nameless"). Ah Ro says that when she looks at him, she feels ashamed and hates herself, and Sun-woo reaches out as if to touch her comfortingly.
But Ah Ro tells him to leave, and he pulls his hand back. He obeys and leaves, and Ah Ro collapses and gives in to her tears.
That evening, the sound of Woo-reuk's gayageum echoes through the Hwarang grounds as Sun-woo watches Ah Ro head for home. Hwa-gong's assistant asks why Hwa-gong agreed to let Princess Sookmyung come to Hwarang, and Hwa-gong just says it was to protect the Hwarang.
Princess Sookmyung stays up thinking about her encounter with Sun-woo by the river. Ban-ryu is also awake, recalling a conversation with his father, Ho Gong, who'd told him that he must prevent the Hwarang from performing at the Moon Festival.
The next day, Soo-yeon complains to a brooding Ah Ro that she's worried about Ban-ryu's safety if her brother doesn't find out that she's the one who grabbed him. Ah Ro complains that she found out her brother isn't really her brother, and she wants him to be, but she hates him because he insists on being her brother. Yeah, that's confusing.
The boys continue practicing their music and dance, and we get a hilarious glimpse of them helping each other stretch. Su-ho hikes Ban-ryu's leg over his shoulder and takes great delight in making him cry out in pain, while Ji-dwi looks like he's trying to split Sun-woo in half (and boldly admits that he's doing it out of jealousy). Yeo-wool and Han-sung just get the giggles, failing to touch fingers over their outstretched legs.
Han-sung gets the okay from Hwa-gong to eat with the rest of the dancers, and Yeo-wool compliments Ban-ryu on his improved dancing. Still thinking that Ji-dwi is sick, Su-ho shares his rice with him, which is pretty sweet.
He warns everyone to do well at the festival because he intends to show the queen regent his loyalty. Yeo-wool snickers that it's not loyalty Su-ho wants the queen regent to see, and Ji-dwi narrows his eyes at Su-ho.
The Moon Festival nears, and Hwa-gong reminds the Hwarang that they'll pass or fail depending on the people's reaction to their performance. Only Su-ho notices that Ban-ryu is nowhere to be found.
Ah Ro finds him brooding alone, but her main concern is Soo-yeon. She asks Ban-ryu if his feelings for Soo-yeon are genuine, and says that Soo-yeon likes him a lot. She holds up another letter from Soo-yeon, and when he sees it, Ban-ryu's expression changes to something that almost looks like hope.
Ah Ro says that if Ban-ryu's feelings are not sincere, then she'll tear up the letter right now. We don't hear Ban-ryu's answer, but next thing we know, he's reading Soo-yeon's letter. Awww. He smiles as he reads that she's looking forward to watching him dance at the Moon Festival, and says that she'll always support him.
The boys gather that night for one last rehearsal, and they do seem to have improved by leaps and bounds. The princess's arrival unnerves them, and Hwa-gong informs them that she'll be staying here for a while to help. One drummer pipes up and asks what the princess is good at, and she confidently steps to the middle of the rehearsal space.
Princess Sookmyung draws her sword and executes a few precise acrobatic moves, all the while holding challenging eye contact with Sun-woo. Woo-reuk starts beating a simple rhythm on the drum as the princess continues her sword dance, ending with a flourish. She then levels her sword at the throat of the Hwarang who asked what she's good at.
The princess addresses the entire Hwarang, and says that she heard this will be their first introduction to the public. She warns that they can't make a single mistake, and behind her, Hwa-gong smiles.
As the town women pretty themselves up so as not to be outshone by the beautiful Hwarang men, Minister Park and Ho Gong also prepare for the Moon Festival. Ho Gong assures Minister Park that Ban-ryu will do as they instructed and ruin the performance.
Ji-dwi visits Ah Ro and attempts to cheer her up, and she sighs that he must be sleeping well lately. He asks if she'll sleep with him if he isn't, cheeky boy. Ah Ro whips out an acupuncture needle and warns him not to even try it.
He asks if she's coming to the Moon Festival, and says that he wants to dance for her. He leaves, and Ah Ro sighs that she's getting tired of hearing him say the same things over and over.
Ah Ro runs into Sun-woo outside later, and steps up to say that he's not her brother. She says she's only staying silent about this because it's a crime to hide a low-born, and because she feels sorry for her father, who's spent years looking for her lost brother.
Sun-woo stops her from walking away, and reaches up to smooth her tousled hair. He asks softly if she's coming later, but Ah Ro slaps away his hand. With one last accusing glare, she leaves, muttering that he's not her brother.
Queen Regent Jiso calls Ji-gong to the palace again to check her health before the Moon Festival. Refusing to look her in the eye, he tells her that she won't be able to sit and watch the festivities for a long time. His expression hardens when her attendant brings her tea, and the queen regent notices and decides not to drink tea today.
Ji-gong starts to leave when Hyun Chu tells the queen regent it's time to head to the festival, but she stops him and asks if he's considered her suggestion that they start over. Ji-gong only tells her to dress warmly.
The Hwarang all dress in their performance uniforms — all but Ban-ryu, and Sun-woo notices that he's unusually agitated. The crowds arrive, including the officials, all preparing to watch the show. Kang Sung, the troublemaker who beat up Mak Mun and nearly assaulted Ah Ro, stops to pay his respects to Minister Park, who comments that tonight should be interesting.
Ah Ro does show up, though she keeps hidden, alternately worrying about Sun-woo and berating herself for worrying about Sun-woo. She runs into Yeo-wool, who drags her back to the tent to help the boys get ready for the show.
There's instant awkwardness, until Han-sung chirps that he needs help. Ha, he looks so pleased to have the pretty lady fastening his belt, though she's busy trying not to get caught staring at Sun-woo.
Ji-dwi leaves, stating that he has an appointment, then Sun-woo leaves without any excuse at all. Yeo-wool notices that Ban-ryu is also missing.
Ban-ryu is in the tent where the instruments are stored, and he takes a knife from his sleeve. But he lowers the blade, seemingly unable to do it, then hides it again when Sun-woo spots him and asks what he's doing. Ban-ryu levels a glare at Sun-woo and tells him to leave before he decides to pay attention to him again.
Hwa-gong addresses the Hwarang and asks if they're ready, and the boys say they are. Yeo-wool raises his hand and tells Hwa-gong that two Hwarang have gone missing.
While Ban-ryu struggles with himself, Han-sung finds Ah Ro bandaging one of the drummers' hands. He says that both Ji-dwi and Ban-ryu are missing, and that they'll all fail if they don't find them in time for the performance. Ah Ro overreacts, worried that Sun-woo might get a second fail, then says it has nothing to do with her.
Still, she goes looking for the boys, and she spots Ji-dwi joining the queen regent in her tent, where she's gone to rest. Ah Ro hears Ji-dwi ask the queen regent why she brought Princess Sookmyung home, and she's shocked to hear Ji-dwi call the queen regent "Mother."
The queen regent sneers at Ji-dwi for lowering himself to dance in front of his people, but he says that it doesn't matter, since nobody knows he's the king. Just as Ah Ro realizes that Ji-dwi is the exiled King Jinheung, she's grabbed from behind by Hyun Chu. He knocks her unconscious and carries her away.
The queen regent informs Ji-dwi that according to Silla tradition, Princess Sookmyung will be his queen. He refuses, stating that he'll choose his own bride, but his mother tells him that his feelings have no bearing on the matter.
As they watch the dancing, Minister Park asks Ho Gong how his task went. Ho Gong says he thinks it went well. What are you two up to?
Just then, the drummers go to get their instruments, only to find that every single musical instrument has been destroyed. Drums are slashed to ribbons, gayageum strings cut, tambourines broken in half.
Ah Ro lies on the floor in front of Queen Regent Jiso, still unconscious. The queen regent confirms that she's Ahn Ji-gong's daughter and that she saw the king's face. Furious, she draws a sword, and points it at Ah Ro's throat.