Tatsumi Oga, a delinquent student at the worst high school in Japan, arrives at school with a small baby who emits massive shocks of electricity whenever it cries. Oga claims he found after splitting open a strange man who came floating along the river, though his friend Takayuki Furuichi doesn't quite believe. Whilst at Takayuki's house, they are both approached by a demon woman named Hildegarde who claims the baby, known as Kaiser de Emperana Beelzebub IV, is the son of Devil King who was sent to Earth to find a human to raise him so he could destroy humanity.

As Ishiyama High holds an assessment test for its studyphobic students, the Great Demon Lord also holds a test for Beelzebub, requiring him to earn points by beating up various things, or run the risk of both he and Oga facing remedial classes in the Demon World. With Beelzebub not showing much hope, Oga decides to try and dump Beelzebub on whoever scores highest on the test. When a rival school interrupts the test, Oga fights them off to allow the other students to keep on the test, earning enough points to avoid remedial lessons, later learning that the smartest student it actually Takayuki. Later, Hilda prepares a letter to the Great Demon Lord, writing reports on Oga, his family and the Tōhōshinki.

Beelzebub gets a summer cold, causing his body to give off incredible heat. As his condition gets worse, the Zebel Spell on Oga's hand disappears, leading Hilda to become frustrated towards Oga for showing little care towards him. As Oga tries to decide what to do, he encounters one of Tojo's henchmen, Shojo Aizawa, who seemingly outmatches Oga before leaving. The next morning, both Hilda and Beelzebub have disappeared. As Oga searches for them, he encounters Tojo with Beelzebub on his back, who challenges Oga to a fight. As the two fight, Oga is shocked to see what appears to be the Zebel Spell on Tojo's shoulder, before he is knocked clean into the river.

Furuichi is woken up by Alaindelon at 4:00 A.M. and is teleported to Ishiyama High to watch Oga and Tojo's fight with Hilda, Lamia, and Forcas Rachmaninoff. Meanwhile, Kanzaki, Himekawa, and Shiroyama confront Aizawa and Karou and begin to fight, but are quickly beaten by them, but they refuse to give up because of their stubborness. Natsume shows up and defeats Karou in one blow, and is about to deal with Aizawa. Kunieda and the Red Tails finish dealing with the delinquents and go to watch Oga and Tojo's fight, with Oga at a disadvantage. Beelzebub activates the Zebul Spell, thinking Oga cannot win, shocking everyone. Lamia accidentally sets off one remaining firework and it's aimed at Oga and Tojo. Oga easily stops the firework and causes a giant flaming Zebul Spell to appear on the ground. Oga orders Beelzebub to not interfere in his fight, promising he will win and Beelzebub erases the Zebul Spell. Oga and Tojo resume their fight, which goes on until dawn, and just as it looks like Tojo is about to win, Oga spins around and performs a suplex on Tojo, winning the fight. Oga tells Beelzebub he won the fight and Beelzebub tackles Oga to the ground. Tojo's past is revealed, showing a man he looked up to who taught Tojo the ture meaning of fighting and had a Zebul Spell on his shoulder, which Tojo got tattooed on his shoulder in order to look like him, and Tojo tells Oga he is now the strongest at Ishiyama High.

In order to make up for forgetting his daughter's birthday, Alaindelon brought Angelica to Furuichi's house for a tour of the Human World. Unfortunately while the gifts were being retrieved from Alaindelon, a Yople alien teleported into the human world and escaped. Angelica resolves to track down the Yople, using a demon wand that transforms its user into a Magical Girl. Gathering 4 other girls - Hilda, Azusa, Honoka and Aoi, they form the 5 Fairies of Light and manages to track down the Yople at an amusement park where Tojo was working as part of the cast in a Gohan-kun theatre drama. A rival girl gang challenges Aoi while they were capturing the Yople and a fight ensures. Eventually, Furuichi manages to pin down the Yople and both of them are teleported away with Angelica's ability. Furuichi eventually returns back to the human world through Alaindelon, leaving him to wonder if he was even inside Angelica at all in the first place. Unfortunately, Angelica left before Furuichi could ask her about it.

The match between Ishiyama and the 6 Holy Knights is here, and this is not your usual volleyball! With their pride and their educational future on the line, the Ishiyama gang puts it all out there on the court! Will Furuichi the Strategist be their trump card?

The episode opens with a distinct sci-fi feel, before moving into the game, where the Ishiyama group are in the middle of getting their asses handed to them. They are unable to do anything against the tank. Then Yuka shows up, driving a giant robot called the Crazy Frog. She crushes the tank, and proceeds to kick and tap dance all over the other vehicles. Up until she steps on a mine and loses the tank. Tatsumi's training goes more like an aerobic workout, complete with lame musical accompaniment. He complains about this, calling out for being an exercise, and not training. Meanwhile the gamers run into more trouble when En's team start using an invisibility cheat. Himekawa realizes what they are doing, and goes to prepare some countermeasures. While Tatsumi does pushups, Saotome tells him that Tojo asked to be trained, and if he isn't careful Tatsumi will be overtaken. Saotome uses a recording of Tatsumi's voice to make a training partner who has all his hidden strength.

When Black Beel has gone missing, Zenjuro urges Oga, Furuichi, and Beel to look for him before something bad happens. Meanwhile, Himekawa who has kidnapped Black Beel for his close resemblance to a lucky statue experiences great luck and wealth. Somehow, Black Beel has grown gigantic.