Episode 27

"Yokai Hunter Amakusa Haruaki Appears! ~The Threat of a Hundred Demons!!~" is the twenty-seventh episode of the Mob Psycho 100 anime adaptation, and second episode of the third season.

Synopsis
Salt Middle School has tasked their students to prepare for a cultural fair, and Mob has teamed up with his classmates Inukawa, Niido, and Sagure to design the costumes for their class' haunted house project. Serizawa has also decided that he will start attending night school.

At the same time, yokai hunter Haruaki Amakusa has made his appearance and seeks help from Reigen in defeating the evil yokai horde called the Hundred Demons, and stop them from resurrecting the Great Yokai King.

Plot
On a dark windy night, Yokai Hunter Haruaki Amakusa stands atop of hill gazing at the Divine Tree and ponders what monstrosities await.

At Salt Middle School, Mob and his fellow students Inukawa, Niido, and Sagure, all of whom have no jobs for the upcoming cultural fair, are assigned to do the costumes for their haunted house. With their desks adjacent, the group contemplates how to proceed with their tasks, and Niido suggests they keep things simple with a ghost sheet. Sagure and Inukawa are on board with the idea; however, Mob suggests more effort be put into their task. On the other hand, Mob starts to stutter when Niido asks what kind of costume would be best, increasing his explosive progress growth to 22%.

Meanwhile, at the student council office, Ritsu objects to the cultural fair themes being promoted at their school. Despite this, Ritsu's objection is overruled by most of his peers, forcing him to accept the fact. Time goes by, and progress toward the cultural fair goes nicely, much to Mob's dismay, who grows ever more anxious by the minute. On Reigen's side, he is considering redesigning his website and Serizawa reveals his plans to him about relearning his compulsory education. Since it's a night course, Reign allows Serizawa to pursue it, believing he'll still have Mob, but wonders where Dimple is. Moments later, Amakusa enters the office and requests Reigen's help exorcising some Yokai. Unable to understand what Amakusa was trying to inform him, Reigen politely asked that Amakusa wait outside while he and Serizawa handled the upcoming next client. Much to Reigen's dismay, Amakusa does so and, when seated, formally introduces himself as a Yokai Hunter. Losing his temper, Reigen chastises Amasuke for using too many buzzwords and demands that he get to the point. So, Amasuke explains to Reigen about a swarm of Yokai called the Hundred Demons seek to revive the Great Yokai King who lays rest somewhere in Seasoning City. Initially, Reigen tries to brush Amasuke off, until he offers him 1mil yen as a consultation fee, and once Mob arrives, he tags along in the Yokai Hunt.

Following Amasuke's lead, Reigen, Serizawa, and Mob are led to several possible places, all of which turn out to be duds, until finally, he points out an abandoned building. Reigen notes how he and Mob once performed a job there where the spirit was already expelled; Mob, on the other hand, is transfixed on his costume issue, but Serizawa senses a weird energy there. Entering the building, Amasuke claims that the building is the site of the problem. Mob's explosive progress growth also increased to 31%.

Reaching the basement of the building that was riddled with tree roots, the group carefully moves forward with the fearful Amasuke leading. Noticing that Amasuke is sweating a lot, Reigen asks if he's alright, whereas Amasuke confesses he's used to fighting Yokai one-on-one. It's then that Reign gets his hand sticky by touching the wall, giving Mob an epiphany of hanging konjac on the walls for the culture fest haunted house. To Amasuke's shock, the pathway they came from was closed off, forcing them to deal with whatever was messing up the area. Mob continues to get ideas for his school culture fest as a Yokai soon attacks them. Making a stand against it, Amasuke protects Reigen and tries to slay it with his sword, only for it to break against it, much to his dismay. Using energy-infused business cards, Serizawa slew the Yokai, only for the group to be surrounded by more of them.

Eventually, the Yokai King and his four generals accost and attack the group while Mob's explosive progress growth also increased to 42%. Thanks to the combined efforts of Mob and Serizawa, the Yokai King and his four generals were beaten. Despite Amasuke offering Serizawa and Mob jobs as Yokai Hunters, they respectfully decline and, thanks to Reigen running his big mouth, blew the chance to earn 1mil for the job they just did.

Finding inspiration from the Yokai King's appearance, Mob and, reluctantly, his other classmates create a costume based on the Yokai King. In the end, their costume is a hit, and on Ritsu's side, he reluctantly acts as a maid where Sho visits him.

That night, Reigen adds that he defeated the Yokai King to raise the page views on his website.

Anime and Manga Differences

 * Conversation between Reigen and Amakusa runs slightly differently in anime.
 * Amakusa offering money to Reigen, and him talking about parents happens only in anime. In the manga, Reigen decides to go with Amakusa, because there is no other way to get rid of him, and he is worried that if he says is true, it can scare away customers.
 * In the manga, the first yokai that appeared was killed by Serizawa, while Amakusa was charging his energy. Then, when more yokai appears, Amakusa breaks his sword in first use. In anime, Amakusa saves Reigen from attack from the first yokai, then breaks his sword while trying to defeat him.
 * Price of Amakusa's holy sword is anime-only.
 * Serizawa fighting with his business cards is anime-only. In the manga, he uses regular exorcism.
 * In the manga, Reigen suggests escaping when Yokai King and four generals appear.
 * Note that Mob's costume didn't leave an impact due to bad lighting was omitted.
 * Teru and Awakening Lab students appear at the festival only in anime.
 * Scene with Reigen updating his website is anime-only.

Notes and Trivia
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