Natsume, Kitamoto and Nishimura take a trip to an old inn to spend some time doing their homework. Surrounding the inn there is a lake in which is believed to live a mermaid.

(Source: Wikipedia)

Natori tells Natsume of a well near the mansion that holds a group of Oni. They are calling out to any Youkai. He also learns that Kai came down from the mountains to free the Oni. While looking for Kai, Natsume sets off one of Natori's traps in the mansion. Kai saves Natsume and heads off to kill Natori. Natsume follows him,to save Natori from getting killed. After he encounters him, he is forced to make an important decision: Which ones are more important to him? Humans or Youkai?

(Source: Wikipedia)

Tanuma's father leaves on a trip and a strange youkai invades his house, spreading miasma that makes all the nearby youkai suffer. Natsume tracks it down and discovers that the noxious youkai was once a resident in an all-youkai village. A portal had opened for a short time during a human ceremony that he had taken his sister to watch. However, they became trapped in the human world, and his sister died. After returning to the old temple where the ceremonies were held, the portal opens and he returns home.

Natsume accidentally bumps into a woman with blood covering her body. He follows the bloody footsteps that the woman left and discovers a small house. When he opens the door, he sees badly injured youkai. There is someone killing youkai for blood, and with the help of Natori, Natsume tracks down who he believes to be the murderer: Matoba. However, Matoba captures him.

Natsume finds out who's been stealing the youkai blood: the exorcist Matoba Seiji. He investigates with the help of Natori, but is captured by Matoba's servant youkai. Matoba is willing to sacrifice any number of youkai for his own ambitions. He tells Natsume why he's gathering blood: to release the seal on a powerful youkai. Natsume learns that there are people who treat Youkai in a totally different way than he or even Natori.

Natsume encounters some strange, monkey-mask wearing demons while out in a forest. They want the book of friends, and start physically threatening him until Natsume is saved by Nyanko-Sensei. Later on, Natsume encounters the demons again and is captured by them, and brought to their forest. Meanwhile, Nyanko-sensei learns some interesting things about the forest the monkey mask demons live in. Running away from the demons, Natsume and Nyanko-sensei are unintentionally saved by an exorcist - Matoba! Not wanting to confront him, Natsume runs again but gets lost in the woods, and stumbles upon a house... belonging to the Matoba. Both he and Nyanko-sensei are captured, but manages to escape and find each other, though being lost in the house. The episode ends with Matoba finding Natsume saying, "It's been a long time, Natsume Takashi-kun.

Natsume and Matoba talk, but when the conversation doesn't go the way he wants, Matoba orders Natsume to be put in a cell. Natsume escapes with the help of Nyanko-sensei. Along with his other demon companions, Natsume helps the monkey-masked demons living in the forest.

In the town Natsume used to live in, a girl recalls Natsume. She remembers his strange actions and wanted to understand him. Meanwhile, Natsume encounters a small Youkai which reminds him of the same girl and town.

Natsume is saved by Tanuma and the two escape from the banquet hall with the help of Natori, who was disguised as a youkai. Tanuma is drawn more into the world of the youkai and experiences it first-hand, which greatly worries Natsume. Blood marks are found all around the mansion and Natsume's fears come true when Tanuma is attacked by Omibashira, but is protected by a stone Natori gave him. After Natsume helps Natori seal Omibashira everyone is able to escape the previously sealed exits. Promising Tanuma that he'd tell him his complaints at school the next day, Natsume finally arrives back home.

Natsume is pretending to be the god Houzukigami, so the moon splitting festival will end with a victory and the mountain will not be ruined. Winning the contest will not be easy, but with help from Natori he will find the way.

Natsume, accompanied by Nyanko-sensei, set out to visit his old home. He visits a relative to pick up the key to the house, but is being followed by a youkai who wants him to draw a mouth for it. He leads the youkai away from the home of his relatives and Nyanko-sensei drives it away. When the two get back on track to finding the house, Natsume is suddenly attacked by the youkai and becomes lost in old memories.

Natsume, possessed by the youkai, thinks of an painful incident from his childhood involving the family he was living with at the time. The youkai offers to eat all his memories, so that he will no longer have to relive his pain.

Natsume finds a letter addressed to him from Matoba. Walking in the forest, he loses it when an amateur exorcist seals a yokai in a pot. Noticing the weak seal, Natsume and Nyanko-sensei take it to Natori's condo to re-seal it. When Natsume returns home he sees Matoba and learns the letter was a request for Natsume to attend a meeting of strong exorcists to weed out the person who has been targeting exorcists.

Matoba brings Natsume to one of the Matoba clan villas to attend the exorcist meeting. Natsume learns that a mask yokai called "Magatsumen" is controlling people and disguises himself as a shiki in order to test attendees if they have been possessed. By following a strange spring sound, Natsume finds the culprit behind the mask possessions and drives the yokai out. Matoba shoots the yokai with an arrow to exorcise it.

Tanuma invites his friends to an inn run by his relatives. While sweeping outside, Tanuma is greeted by an old woman named Ito-san. Natsume learns that Ito-san is a yokai that serves the Mizunagi shrine by protecting the mountain festival. Ito-san has come into the inn because another yokai has stolen the festival's white mask and has disguised itself as an inn guest. Natsume finds the yokai who stole the mask for the festival's power, and Ito-san exorcises her. Ito-san warns Natsume to keep her identity a secret until after the festival is over so she can complete the festival. Natsume says he will tell no one she is a yokai so she can stay in this town as long as possible.

Natsume encounters a pair of youkai who make cups that turn sake delicious. Their power is waning, and they've come to a spring that's said to restore spiritual energy. But the spring is occupied by a monster...

Natsume's old classmate Shibata (from "False Friend" / "Itsuwari no Yūjin" (偽りの友人)) calls. Natsume visit Shibata together with Tanuma, where Shibata tells them about the "Doll Mansion of Sotogi". A youkai from the mansion later attacks them.

A competition is opened to search for a famous researcher's sealed room. The prize are his research books, and many exorcists are gathered. Natori is invited, Natsume wants to help as this might mean finding something that might let him find information about the Book of Friends.

Natsume decides to tell Natori about his secret, when the search for the seal room is over...

Natsume encounters an old man who asks for help with getting home. The old man turns out to be a yokai who will soon disappear and he asks Natsume to help him to fulfill a promise that he had made.