Theo Tan and the Iron Fan

A Chinese American boy and his snarky fox spirit face down demon kings as they race against time to be reunited with his brother's spirit in Theo Tan and the Iron Fan, Jesse Q. Sutanto's magical, action-packed sequel to Theo Tan and the Fox Spirit.
Theo Tan and his fox spirit, Kai, are willing to go to hell and back for their family. Literally.
After exposing the corruption at Reapling Corporation and trapping the demon king Niu Mo Wang, they learn that Jamie (Theo's beloved brother and Kai's first human master) was not allowed to move on after death, and is now trapped in a waiting room in Diyu.
If they can reach his soul before it faces judgement on the solstice, they might be able to convince King Qingguang to send his soul back to earth! Still, a trip to Diyu is no easy matter, and Theo and Kai can't do it alone. Fortunately, they have good friends who are happy to help.
But even with Namita's knowledge and Danny's powerful dragon familiar, the odds are stacked against them. Can Theo and Kai's new bond hold up against lying demons with grudges, impatient Kings of Hell, and the wrath of the demon king's powerful wife, Princess Iron Fan?