Modern-day office drone Zou Yan accidentally stumbles into the world of cultivation and wakes up as Liao Tingyan, a disciple of the Qinggutian Sect. She's soon selected to serve the reclusive Grandmaster Sima Jiao, a powerful cultivator who's been secretly sealed inside a mountain for 500 years. Twisted by isolation and rage, he's cold, hot-tempered, and bent on revenge. Liao Tingyan doesn't know that "her" original identity is a demonic assassin. But to his surprise, she shows no ill will, no ambition, and no desire at all. Her nature fascinates him. Thus begins an unlikely romance between a villainous immortal and a healing-type "slacker," a connection that defies fate and spans lifetimes.

The movie focuses on the battle of Cheolwon, where the 63rd Army of the Chinese People's Volunteer Army (CPVA) was ordered to enter the battlefield of Cheolwon in May 1951, just after a month-long battle, to fight against four divisions of the United Nations Army (UNA). The volunteers fought with bloodshed and finally brought the enemy to the negotiation table.

The exceptionally gifted Ghost King, He Simu, unexpectedly encounters the young general, Duan Xu, while out on a break, searching for food. This young general, who carries an item belonging to someone from He Simu's past, seems not to be the real Duan Xu. As they test each other through subtle exchanges, He Simu gradually uncovers the dark past and aspirations hidden within Duan Xu’s heart. In turn, Duan Xu discovers the steadfastness and loneliness that He Simu has endured. Despite the fleeting lifespan of a mortal, no more than a hundred years, and the four-hundred-year-old ghost who still retains the appearance of a young girl, they resist the relentless passage of time through their love.