In a world divided between the celestial realm, the human world, and the netherworld, humans live alongside greedy demons and the immortals known as sages who protect them from harm. Feijin, a half-fox-demon half-human, loses his family at a young age and is taken in by the sage Gaochun, who raises him as a disciple. Over the centuries, Feijin’s admiration for his master deepens into romantic love, but a relationship between a master and pupil is strictly forbidden. Despite repeatedly confessing his feelings, Feijin is gently turned away each time.

Driven by desperation, Feijin uses a spell to put Gaochun under a trance and forces a physical union in the bedchamber. The encounter reveals a side of Gaochun that Feijin never expected—passionate and experienced—and afterward Feijin learns the reason. Gaochun once fell deeply in love with a demon named Shui, a relationship that broke the laws of the immortals. As punishment, Gaochun received a permanent scar on his back, and he and Shui were forcibly separated, with Shui sealed away. The forbidden night with Feijin causes Gaochun to lose his immortal status and become a disembodied soul, forcing him to reincarnate in the human world.

Determined to find Gaochun, Feijin descends from heaven and searches for centuries. He encounters a young boy who carries the aura of Gaochun’s soul and begins to form a new bond. Meanwhile, the seal on Shui weakens, and the demon returns to reclaim Gaochun. Shui takes Gaochun to the netherworld, and Feijin resolves to bring him back. To gain allies, Feijin seeks out Gaochun’s beloved younger half-brother, Gaoliu, a prince of the human kingdom. However, Feijin’s mission becomes entangled with political intrigue when he is captured by Gaoliu’s scheming secretary, Huanrong, who forces Feijin into a deal to seduce Gaoliu in exchange for his freedom. Feijin reluctantly complies, and a complicated relationship develops between him and Gaoliu, further testing his loyalty to Gaochun.

Overlapping these central threads are the stories of other couples: Gaoliu’s father Tianlei and his son Xinshao, whose ambiguous affection hints at a darker bond, and the secretary Huanrong with the prime minister, whose own painful past drives his schemes. As Shui fully revives and Gaochun’s memories remain clouded, Feijin must navigate forbidden love, brotherly rivalry, and the treacherous power struggles of both heaven and the human court, all while racing to reclaim the master he has loved across lifetimes.