As a girl named Harumi ends up sneaking into their school with her friends, she soon finds the faces of her friends have mysteriously vanished. When Harumi nearly drowns in a pool while trying to escape, she is rescued by a kappa named Kappaeru, who takes her to an underground base where she meets also meets the ice princess Yukiko and the fiery mage, Enma, who together form the Yōkai patrol, a group sent from hell to stop demons that appear on the surface. Determining the culprit is a face-eating demon, Harumi offers to lure out the demon so that Enma and co can attack it. Although Harumi finds the beast, due to Enma's laziness her face is also stolen by the time they arrive. Enma ensues in battle with the demon and, despite showing no disregard to the innocent faces while smashing it with his fiery hammer, manages to kill the demon and return all the faces to their rightful bodies.
While Harumi and her class are on a school trip to an amusement park, they are attacked by a Squid Demon named Walter Geso. Despite taking Yukiko hostage as well, Enma manages to free all the hostages and defeat the demon, albeit destroying the park in the process. Afterward, Yukiko and the others explain to Harumi how they were summoned by the Great King Enma, Enma's uncle, to travel to the human realm to stop escaping demons. Their first case involves fighting demons named Snakejar and Shock Willow. After the flashback, Harumi reveals that he teacher, Ms. Chiko, had been acting weird recently, and upon investigating her, they find a strange mark on her leg.
After learning that Ms. Chiko had been infected poisonous smoke from a demon known as Dokuro, designed to make her ripe enough to eat in three days, Enma engages her in battle but is forced to retreat before he can remove the poison. With the third day approaching, the Yokai patrol decide to have Yukiko take Ms. Chiko's place. After Yukiko and Harumi carefully obtain Ms. Chiko's underwear to wear in order to complete her disguise, Dokoro appears and is quickly finished by Enma.
Harumi falls unconscious after finding a strange cat. Yukiko brings them both into the lair, but she ends up being put to sleep too. Chappeuji concludes that this is a work of a Yokai named Nekomu, who puts humans to sleeps and messes with their dreams. Enma attempts to use some rather dubious means to wake Yukiko up, but he and the others end up falling asleep too, ending up in a dream world where everyone is forced to boogie. They soon learn that a huge demon is gathering together the unconscious humans and turning them into yokai. Nekomu attempts to stop them from waking up, but Enma takes advantage of the fact he's in a dream to make himself into a mech which slices off Nekomu's tail, allowing everyone to wake up. Enma then proceeds to kill the demons which reverts everyone else to normal. Afterwards, they spot one of the culprits behind the plot, the mysterious witch, Enpi.
Whilst trying to find the Yokai Patrol concerning a case of bees causing people to become brainless, Harumi spots Enpi talking with the beehive demon behind it. Although Enma manages to outdo the demon, he and Kappaeru get distracted keeping a bee out of Yukiko's yukata and get stung, reverting their brains to infant-like states. As Yukiko and Harumi's attempts at taking over the main hero role fail, the demon challenges them to a series of events, promising to restore everyone's brains if they win more than half of them. However, during one of the events, the demon ends up ticking off Enpi and gets beaten up, allowing Yukiko the chance to reverse the nature of Enma's flame stick and kill the demon. They later return everyone's brains, only to get them mixed up.
As a new student named Goro Goro enters Harumi's class, various people, including Harumi and Kappaeru, find themselves inflated into a blimp-like form with an insatiable appetite, with anything they touch also becoming fat. As the Yokai patrol lure out Goro Goro, whose real identity is a Yokai named Fukurashiko, they are ambushed by Enpi and turned fat as well. They end up bouncing all over the world, eventaully ending up on the moon, where Enma, Yukiko and Enpi, who was also made fat, simultaneously kill Fukurashiko, returning everyone to normal.
The world is struck with a phenomenon that causes people to constantly fall over in a comedic way, forcing them to crawl in order to get anywhere. As Enpi denies having any part of this, her pratfall leads to awkward situation for her and the Yokai Patrol whilst at a zoo. Just then, the yokai behind the mess, Sutendouji, revealing that Enma and Enpi are siblings and that he plans to steal Enpi away, attempting to take the Blaze Circlet on Enma's head as a wedding ring. He reveals that the circlet used to be worn by Enpi, but suddenly ended up on Enma's head, which led to Enpi becoming a streaker. Enma fights off Sutendouji and beats him, only killing him by accident. Afterwards, Enma contacts the Great King Enma to ask about the circlet.
The school is covered in snow and the Yokai Patrol is attacked by a group of demons, but Enma is too cosy under his kotatsu to do anything about it. They attempt to remove the Blaze Circlet from Enma's head, but Enpi arrives, telling everyone that if it's removed, Enma's full power will be unleashed and destroy the world. As Enma becomes traumatised by memories of his parents, the demons try cornering Yukiko, Harumi and Enpi, but end up getting themselves killed. After the battle, Enma recalls his promise with his parents was to be a good boy so he could get a load of chogokin toys which never came.
