Asumu Adachi and his mother went to Yaku Island for a family reunion. During the boat ride to the island, Asumu meets a man named Hibiki, who has just saved a child from going overboard. On Yaku Island, people are disappearing in the forests and Hibiki goes in to investigate. In the forest, Asumu and his cousin meet Hibiki and also run into a pair of demons known as Douji and Hime of the Makamou. Hibiki goes to fight the Makamou and transforms into an armored figure called an Oni. When cornering one of the Makamou, Hibiki is seen by Asumu.

Hibiki spends the night at the memorial where Asumu is staying. The next day Asumu meets Hibiki out by the beach and they both talk about what Hibiki does for a living. Asumu witnesses Hibiki transform into the Oni to fight the Hime and her child, a demon-spider called Tsuchigumo. After the fight, Asumu begins to take a liking to Hibiki.

Both Asumu and Hibiki return to Tokyo where Hibiki is sent off to defeat a Yamabiko sighted at Okutama. Later on, Hibiki meets Asumu's mother, who is ecstatic to see him. The strain of studying for entrance exams begins to trouble Asumu as he worries about Hibiki and how safe he is with the type of job he has.

Asumu trails an old man whom he believes has connections to Hibiki after he sees him save a young girl. Elsewhere, Hibiki continues his battle with the Makamou who had been killing people in the forest. After the battle, Hibiki and Kasumi return to Tachibana's sweet shop, where Asumu and the old man are.

Hibiki and Asumu have a talk about the school that Asumu wants to go to. At school, Asumu is told by a teacher that if he fails his entrance test to Johnan, he will have no second chance so he must not fail. Hibiki is then told of a Makamou, called Bakegani, that has been attacking ships and defeated a fellow Oni, Zanki. He goes to fight the Hime, but was overcome by the Bakegani and is forced into the sea.

Ibuki, thinking Asumu is Hibiki's student, takes Asumu to where Hibiki and Kasumi are located. Hibiki and Asumu have a discussion about life and the challenges that everyone faces, leaving Asumu with a renewed passion to do well on his entrance exams. Hibiki then returns to battle the Bakegani that defeated him previously.

Ibuki appears and mistakes Asumu for Hibiki's student, taking him to the sight of a battle. Asumu then joins Hibiki and Ibuki on a trip to defeat an Ittanmomen at Okukuji, where Asumu meets Ibuki's student: Akira Amami.

An irritated Akira tells Asumu that he will only hinder Hibiki if he continues following him around and that it would be best for him to leave. Asumu wonders just how true her words are and asks Hibiki himself how he feels about it. Ibuki then defeats the Ittanmomen and Akira and Asumu make amends with each other.

Spring break has started and Asumu has already gotten off on the wrong foot, having missed going to the movies with his friend. He spends the rest of the day wandering around town and eventually encountering shoplifters. Hibiki looks to see if his training paid off by taking down an Ooari. Ibuki and Akira track down a Makamou that seems to be a little more than they had suspected.

Asumu continues to wander through town after being a witness to the shoplifting, not really sure of himself and what to do next. Hibiki and Ibuki team up to take down a very rare Makamou, Otoroshi.

A new school year has started and Asumu enters high school but still has mixed feelings on the path of life he has taken. Through all the aimless wandering he finds himself back at Tachibana's Sweet Shop. Hibiki travels out to the countryside after a call about people strangely disappearing.

After going through a false wall in Tachibana's Sweet Shop Asumu stumbles upon the Oni R&D room where Midori shines some light on Hibiki's past. Hibiki encounters a Douji and Hime that have unique armor and can't be beaten like the ones he's previous faced.

Hibiki goes to Asumu to ask him for a favor but Asumu doesn't seem to be feeling well. After being given a power boost an Ubume Douji goes berserk, killing the Ubume and the Hime, and proceeds to hunt down other Makamou.

Asumu is hospitalized and undergoes emergency surgery after collapsing in class, his high school life comes to a halt until he heals. Hibiki and Ibuki team up to track down and destroy the berserk Douji.

Asumu returns home after spending a week hospitalized and begins his recuperation. Elsewhere, Zanki reveals that he will soon be retiring and expects his apprentice Todoyama to take his place, a revelation that Todoyama is less than pleased with. Even more, they are called to aid Sabaki at Tsukama Village, where a Yamaarashi is running rampant.

Zanki and Todoyama come to Sabaki's rescue after being captured by the Yamaarashi. Zanki begins to weaken and proves unable to defeat the Yamaarashi. Todoyama takes Zanki's place and destroys his first giant type Makamou. As Zanki retires, Todoyama refuses to take his name, instead wanting to make a name for himself, Zanki dubs him Todoroki, the roaring Oni.

Kasumi and Ibuki go clothes-shopping on their day-off. After shopping and during their meal, Ibuki sees a Douji and Hime pair in the city and begins his pursuit. Elsewhere, Hitomi is having mixed feelings about Asumu and Akira spending so much time together. After defeating the Douji-Hime pair, Ibuki is attacked by an Oonamazu stomach. After its retreat, Ibuki calls Akira and asks her to bring his Reppu.

Akira makes her way towards the ever-changing location of the Oonamazu. Asumu then heads to Tachibana's and ends up helping Hinaka deal with the influx of customers. Later, Ibuki once again takes on the Oonamazu stomach, only to be severely burned by its stomach acids. As she heads towards the battle, a puppet-type Makamou causes Akira to collapse under a bridge. Ibuki then proceeds to fight the Oonamazu for the final time.

Asumu begins his first day at Tachibana's Sweets Shop and discovers that Todoroki and Hitomi are related. Todoroki continues to fight the Bakegani as Kasumi notices something is wrong with him. Zanki later arrives after he is called by Ichiro to examine a recording of Todoroki's peculiar fighting style.

Zanki visits Todoroki on the battlefield to question about his style of fighting. Asumu begins to have troubles at Tachibana's and is then pulled into a conversation with Ichiro about the Oni. Hibiki later joins Todoroki in a fight against an Amikiri. Zanki later makes a decision about his and Todoroki's future.

Ibuki and Todoroki, separately, are following two groups of Makamou that are heading towards Mount. Asama. The oni find it strange that the Makamou don't want to fight nor do they attack humans; what is at the top of the mountain that draws them? Hibiki enjoys a day off of fighting to run errands with Asumu.

Ibuki and Todoroki combined their strengths to defeat the pair of Douji and Hime, but the Ubume and Yamaarashi are nowhere to be found. What they do find is something like the two Makamou but cannot be defeated by their string and wind Ongekis.

Hibiki takes Todoroki to his mountain top training temple to teach him how to play the taiko. Unfortunately, the training seems to be too intense for him. Asumu is assigned the whistle in his high school's brass band and is not too pleased with not having the chance to play the drums.

Hibiki and Todoroki's training is stopped midway because they get a call that a villiage nearby has been attacked. They arrive to the seen and realize that the Makamou is a self multiplying Dorotabou, which can only be defeated with the taiko based Ongeki.

After Sabaki is defeated by a Kappa, Hibiki is sent out to finish the the job. Asumu, Hitomi, Hinaka, and Todoroki enjoy the day off by going to a water park. At the park they run into Tsutomu Tsumura, who works at the park but has ties to the Oni world.

Everybody is out, either enjoying their day off or hunting down Makamou, leaving Asumu and Akira to tend to the sweet shop. Ibuki crosses paths with a strange couple that are dressed in full kimonos in a busy city. Hibiki and Todoroki track down a Bakeneko group hidden deep within a mountain forest.

Hibiki, Todoroki, and Zanki track down the group of Bakeneko hiding in the forest shrine. Tsutomu reveals his relationship to the Oni world to Asumu and asks what he wants to do in the future.

After being beaten up by the shoplifter (first seen in A Squirming Evil Heart) Asumu loses his normal cheerfulness. Hibiki sees this and decides to take Asumu for a forest hike. Eiki is defeated by an armored Douji and Hime; Ibuki and Todoroki are called in to avenge their fellow Oni.

Asumu slips and falls while descending a hill causing him to loose his cellphone and Hibiki to loose his cowboy hat. Asumu blames himself and Hibiki confronts the boy about being too negative and self-consciousness. Ibuki and Todoroki combined their efforts and battle the Yoroi Tsuchigumo Douji and Hime.

A new boy has transferred to Asumu and Hitomi's school, Kyosuke Kiriya. Kyosuke is good at everything from language to sports and makes Asumu feel boring. The Man creates a new Makamou that does not have a Douji and Hime; it wreaks havoc in the busy metropolis.

After talking to Kyosuke Kiriya, who lost his father in a fire, Asumu goes searching for his own father. Kyousuke follows Hibiki and, after seeing him defeat a Makamou, looks to surpass him.

Kounosuke Kogure, a strong-willed arms developer, comes bearing a gift for the Oni who work at the Tachibana Sweet Shop: the Ongekizofukuken Armed Saber. Unfortunately, the weapon is too powerful for a normal Oni and the repercussion for trying to use it is losing the ability to transform into an Oni.

After losing the Ongekizofukuken Armed Saber to the Super Douji and Hime, Hibiki and Todoroki lose the ability to transform. They find out that they will regain the ability to transform in one month, but that is too long with a Kamaitachi running amok. Kogure suggests that the two Oni undergo a special training, under his guidance, to regain their powers.

Todoroki and Hinaka's birthday date goes awry thanks to Todoroki's clumsiness and Todoroki feels that he doesn't live up to Hinata's image of an ideal man. Todoroki's love life problems begin to affect his job as an Oni. Asumu sees Hitomi give a love letter to Kyosuke Kiriya and wonders if this is the end of the special friendship they shared.

Todoroki is in a slump after failing to get back together with Hinaka, Zanki comes to the aid of his depressed pupil. Ibuki comes across Kasumi with another man and becomes heartbroken, much like Todoroki. Seeing his team fall apart Hibiki has no choice but to intervene in their love lives, a subject in which he is not too diverse.

A mysterious Armor of the Ogre, that gives the wearer the power of an Oni, has been stolen from a shrine. The thief uses it to attack Oni and Makamou alike; leaving the Oni wander what is the thief's motives for using the armor. Akira starts wondering if the hatred she has for Makamou is really a bad thing and if she should throw away her school life and dedicate her time to becoming a full-fledged Oni.

Having obtained Todoroki's Henshin Kigen, Shuki proceeds to fullfil her vengeance against the large and elusive Notsugo, even if that means endangering her fellow Oni. Ibuki is burdened with eliminating Shuki as punishment for her past crimes against Oni.

Hibiki, Todoroki, and Ibuki encounter a powerful Makamou who is immune to all three of their Ongekis. They choose to retreat and come up with come measure to combat it. Ibuki becomes worried about Akira as he as not seen here since she left with Shuki. Asumu frets that his life is worthless after being kicked out of his high school's brass band club.

Hibiki is defeated by the fearsome Yobuko and becomes bed ridden at the Tachibana Sweet Shop. Ibuki searches for Akira, but is lost and doesn't know what it means to be a mentor. Todoroki is severely depressed after seeing Zanki pep talk Ibuki and he cannot overcome the feeling that he has been replaced as Zanki's student.

A mysterious forest appears in the middle of a rice field and devours any and all who step foot in it. The forest worries the Onis as well as the Man and Woman. Kyousuke decides to ask each of the Onis that work out of the Tachibana Sweet Shop to be their student after being turned down by Hibiki.

Asumu and Kyousuke are both scolded after Akira takes them as students, but they refuse to give up of becoming Onis. Ichirou Tachibana is warned by the Man and Woman that the mysterious Kodama forest could be the beginning of the end; it is know in history as the harbinger of destruction.

With Orochi approaching the number of Makamou are sharply rising, so much so that it is too much for the Oni to handle. Asumu and Kyosuke start their Oni training under the tutelage of Hibiki.

A brutally beaten Todoroki is rushed to the hospital after being crushed by an onslaught of Makamou. He has to go under surgery for any hope of staying alive. Hibiki continues to train Asumu and Kyosuke. It seems that, in the race to become Hibiki's student, Kyosuke keeps falling further and further behind.

After continuously falling short in training Kyosuke gives up on being Hibiki's student. Todoroki, in his current battered condition, looks like he can never again become an Oni. His mentor, Zanki, steps up to take his place and fight against the ever-growing horde of Makamou.

Asumu tracks down Kyosuke where he confronts him about stealing the Oni tool and using it for revenge. Being on borrowed time, Zanki continues to fight Makamou. Todoroki, still rehabilitating from his injuries, must muster all his energy to fight alongside his master in what could be Zanki's final battle.

The Man and Woman lead the Onis to a stone that holds the key to sealing off Orochi, but the task maybe too great for them to handle. Kyosuke becomes more serious about becoming an Oni to the point that it consumes him. Asumu, on the other hand, questions himself on what does it mean to put your life on the line for others.

After thinking about what it means to die without any regrets Asumu decides that he must walk away from becoming an Oni. Ibuki prepares to put his life on the line to bring the Orochi to an end.

With Hibiki at the helm the Onis stop Orochi. This episode takes place a year later where Asumu has detached himself from the Tachibana Sweet Shop and all those who work in it.