When Hwa Yun-seol, the Sage King, was born after 300 years, the celestial realm erupted in celebration. However, on earth, Yun-seol was merely a young child, and no human knew of the Sage King's birth. Thus, the Jade Emperor summoned Kim Da-hye, a human and the master of Surindang who had recently given birth to a daughter named So Eun-chim, to mend the long-severed path to heaven.

The immortals who descended via the mended path were shocked to find that the Sage King was a girl! The celestial realm was in an uproar, but they were soon calmed by her ability to immediately master and use whatever she heard. At the ceremony where the Sage King chooses her spiritual beast, Yun-seol stroked a white tiger. Though it was the newborn spiritual beast of a Sage King not yet a year old, and thus quite small, a spiritual beast was still a spiritual beast. It was the White Tiger, the Guardian of the West among the Four Guardians. It was a choice befitting a Sage King.

Meanwhile, while all the immortals were focused on Yun-seol, there was one person sitting quietly in the corner... her name was Guest, the twin younger sister of the Sage King Hwa Yun-seol. While Yun-seol was always beaming and full of curiosity, she sat quietly reading books, a genius who learned things on her own before even being asked. But as the twin of the Sage King, that talent had to be suppressed. No one bestowed a blessing upon her, and no one sought to connect her red thread of fate. What use was being a genius? Unlike the Sage King, who could instantly utilize a power just by seeing it once, the twin sister understood it in her head but could not use it properly, and its power was significantly weaker. She was the Sage King's shadow, and the two were already bound by the ties of family, never to escape. How long would this tragic fate continue?

Elementary school, middle school, high school. Class president Hwa Yun-seol, vice president Guest. Student council president Hwa Yun-seol, vice president Guest. Ranked 1st in the school Hwa Yun-seol, ranked 2nd Guest. In everything, Guest was outstanding, but a slip of the tongue or a stomach ache—everything conspired to crush Guest in her competitions with Yun-seol. Nevertheless, there was one place where Guest could lean. In her early childhood, which she couldn't even remember, on the day the Sage King's spiritual beast was chosen, all the divine beasts ran toward one spot to be selected. However, only one looked toward the Sage King's shadow. The Black Tortoise, the Guardian of the North. The Black Tortoise of a new generation born after 500 years chose to stay by Guest's side and become Guest's divine beast.