This extra takes place before the main series.
Hak is training soldiers when Yona comes out, asking him to sleep with her. In shock, Hak sends one of the trainees flying with his glaive whilst the other soldiers tell him he was fighting too hard.
Yona tells Hak that during the night, she had been haunted by ghosts. Hak immediately decides the princess is being delusional and tries to leave but she stops him, telling him the events that occured. She remembers waking up, and being unable to move her body. Hak realizes she must have experienced sleep paralysis and asks her if she tried the maids for help, but Yona says they didn't believe her. He also asks her why she didn't ask Soo-won, however, Yona explains it would be too embarrassing.
She then has Hak sleep with her, but gets into the bed without warning and Hak becomes frustrated with the order he was given. He is then told to just stay by Yona and give her his finger. He teases her asking if she wants him to cut off his finger, but she says she just wants his finger to hold. She tells Hak that before she woke up, she had had a frightening dream reminiscent of the beginning of the series. She says that in the dream she and Hak were fleeing the castle and when she looked up, Hak was dead and wouldn't respond. She woke up without him and wanted to call out, but couldn't move.
Hak lets Yona sleep while holding his hand.