The story follows the endless strife between humans and demons, both driven by desire in their pursuit of the mythical Yuli Spring. Carefree and quick-witted, the young girl Xiao Yao unexpectedly embarks on a fantastical journey through the Valley of Ten Thousand Demons, throwing the demon realm into chaos. Revered by demons and feared by humans, the Demon King Hong Ye reemerges to protect the valley. Weathered by time and having seen through the flaws of all beings, he knows the Yuli Spring embodies the corruption of desire. Yet through his encounters with Xiao Yao, he gradually realizes the preciousness of her pure heart, untouched by greed. Together, they face bizarre cases and formidable, mysterious enemies…