At The End Of The Blue Dawn

Ja-Yun has willingly agreed to become her mentor Cheong-Un’s weapon in his quest for revenge. As Ja-Yun participates in the Emperor’s concubine selection ceremony, the Crown Prince appears, turning the entire situation upside down. The Crown Prince, who suspects Ja-Yun’s true identity and stands in her way, and Master Cheong-Un, who can only watch from afar. Amid a journey of vengeance to bring down the Emperor, a bitter and brutal love triangle involving these three begins!(Source: KakaoPage, translated)