The protagonist, Shen Yan, is an heir to a family of chuma xian spirit mediums in Harbin. His grandmother was a top-tier star among the Northeast's chuma xian mediums, with all five spirits in her altar: the Fox, Yellow, White, Willow, and Gray Immortals. After she passes away, only the Gray Immortal, Grandpa Gray, stays with him. He binds himself to a Chuma Sign-in System: signing in earns him talisman paper, blessings from the immortals, and incense points. Incense points can upgrade his altar, unlock the immortals' ability to take human form, and let him summon them into battle.
The setting stays true to Northeast China's chuma xian folk customs: whether an immortal possesses someone depends on fate; the stronger the incense, the stronger the immortal. Chuma xian mediums save people not for money, but for incense. Evil spirits are divided into four ranks: lonely ghosts, baleful corpses, demons, and foreign evil cultivators. The higher their rank, the harder they are to deal with.
