Beelzebub IV

is an infant demon lord, and the son of the Great Demon Lord.

His full name is.

This is sometimes further abbreviated to:
 * Beelze-sama (Lord Beelze) is a term used by Alaindelon and most of the fellow demon servants, sometimes used by Hilda if there's En and Beelzebub is not around during Akumano Academy Arc.
 * . The suffix "-bo" indicates a baby. The "Beel" syllable is pronounced with a short 'e', not a long 'e' as English readers may infer from the double vowel.

Appearance
Beelzebub is a baby with an abnormally wide build and green hair. Beel is almost always shown with his binky, save when he is being fed. Usually, he is seen nude (even in public), causing ordinary people to talk about him and his "parent" Tatsumi Oga. Partially due to Hilda's misdirection, the rest of the Oga's family believes that Beelzebub is Tatsumi's biological son, using their similar eyes (usually frozen in either a blank stare or an intimidating glare)

Personality
Baby Beel is very easily impressed, especially by strong people since he himself is still weak and loses to other babies as well as to cats. On the other hand he is not the smartest one out there and tries to force his way through the most simple problems. It is also shown that he is afraid of insects. He often displays a fondness for things that might frighten "normal" babies, such as violence, exposed muscle tissue (on an anatomy model), heavy metal music, and demonic toys.

Baby Beel used to be a crybaby who used to cry and shock Oga all the time, but as the time goes on he gradually becomes braver to a point where he is now rarely seen crying at all. This is due to Oga's continuous teachings about what it is to be a man and a Demon Lord.

Despite having his own sense of pride and power, Baby Beel can be very shy around girls who are around his age, most notably Futaba Kanzaki and Chiyo Aiba. He tends to listen and follow the two out of apparent fear, perhaps intimidation of them. When around either of the two, he has even demonstrated embarrassment at the fact that he's always nude around them, something that generally doesn't bother him in the slightest.

Tōhōshinki Arc
Beelzebub came to the human world inside of Alaindelon. He was practically drawn to Oga Tatsumi from the beginning and is usually seen clinging to his back. Oga in turn did and still does not want to keep him around since he only causes him problems with other strong people at his school.

Oga tries to give him to Kanzaki, but later Oga beats him up for the disrespectfulness to his comrade. Next day he faces with the serious problem from Beel. Beelzebub pees up like flood with his ability and Oga cries over his fortune again. They encounter the problem with an equipment from the demon world for two hours or so.

Beelzebub and Oga head out to a department store to get the Diapers, so the pee of Beezebub would be stopped. They encounter a gang of robbers named as Orz3. Beelzebub gets attached to one of the Robbers, but Oga, feeling uncomfortable over the behaviour of robber, kicks him out. Beelzebub starts to pee again, but later Hilda takes them along to the ocean before Japan can be flooded.

Prince En Arc
When others are looking for En in online games, Beel and Tatsumi are spending time training to become stronger.

Return to Ishiyama High School Arc
Baby Beel drinks from a milk bottle while Oga is having breakfast with his family. It is suggested by Oga's Mother that he goes to a "trial" nursery school that has recently opened up nearby. Oga's Father supports the idea; while trying to use Baby Beel's age as a reference, he realizes that he does not know it, and evidently, neither does Oga himself. Baby Beel accompanies Oga while he learns from Hilda that Baby Beel is two years and nine months old. He continues clinging on to Oga's shoulder while he talks with Furuichi about the "trial" nursery school sometime after. After some time, the three head outside so that Oga can prove that he and Baby Beel can stay further apart from one another; as it turns out, rather than fifteen meters, they can now stay apart for at least eighteen.

Baby Beel later goes to the "trial" nursery school with Oga and Furuichi. When it is announced that the children will be partaking in an activity together, Oga sets Baby Beel on the ground, telling him to make new friends.

While everyone is dancing, another toddler named Raita slaps Baby Beel on the cheek, nearly causing him to cry. When the principal of the "trial" nursery school attempts to intervene, Baby Beel speaks out to him, apparently telling him not to get involved, as he will take care of things himself. The principal then has Baby Beel and Raita build a train set together; however, Raita continues his bullying tendencies, stealing one of the trains away from Baby Beel, even telling him to construct the railroad tracks instead. Baby Beel surprisingly shakes it all off and begins picking up some of the railroad parts. As it turns out, all he has been thinking about is making new friends in the "trial" nursery school, which is why he is being unusually cheerful.

Later in the afternoon, Oga and Baby Beel head home together, where they are confronted by Raita and his older brother, who both taunt them for their behavior at the "trial" nursery school; however, the two siblings eventually realize who Oga and Baby Beel really are. As Raita's Brother goes in to punch Oga, the child-rearing gang leader tells Baby Beel that he will show him how to make friends, and he ends up sending Raita's Brother several meters away, with an additional warning.

Baby Beel sleeps peacefully on the morning of the new year. He later attends a small festival held at the Kunieda residence with Oga and Furuichi where they pray to the Gods, albeit in a more informal manner. Afterwards, they all enjoy s small meal with Oga feeding some of his own food to Baby Beel. Oga and Furuichi eat with Aoi with whom they also inform about a strange dream that Oga had in the morning. Unable to interpret its meaning, Aoi suggests that they open some fortune cookies, though Oga's message simply reads "radish", to all of the males' confusion.

On the first day of the new semester, Baby Beel, as usual, accompanies Oga and Furuichi to the reconstructed high school. The three re-affiliate with the high school throughout the morning and even learn from some, particularly Natsume and Himekawa, about how there are newcomers who are targeting Oga.

One of them, Nasu, has already introduced himself to Oga, which later results in the child-rearing gang leader seeking him out. He and Baby Beel find him in the hallways near Kanzaki's gang. Baby Beel draws whisker-like features on Nasu's face with a marker when he comes close to the duo. Subsequently, per Oga's suggestion, the new freshman punches Oga and sends him flying into the ceiling, effectively burying his head, as well as Baby Beel's, into the concrete.

Baby Beel manages to poke his head out. He rubs his face and then starts shouting at Nasu, only to be shot a dark smile at the latter, frightening the young Demon. Moments after, Oga frees both of them from the ceiling, and he lands on the ground while holding Baby Beel's leg. Baby Beel later returns to his spot near Oga's shoulder and watches as the following events unfold. Shortly afterwards, several of Nasu's allies arrive to take him away, and he leaves with them, but not before warning Oga that he will take Baby Beel away from him.

With Nasu's leave, Baby Beel suddenly starts pulling on Oga's hair out of frustration, which Furuichi suspects is because of the stress and tension that he has been feeling earlier, something originally noted by Oga himself. Baby Beel eventually stops after two other delinquents, Ebian Ichikawa and Kankurō Akahoshi, give their warnings to Oga before leaving the vicinity.

Baby Beel later returns to the Kunieda residence with Oga and Furuichi during the afternoon. There, he gets into another childish fight with Kōta, until he later "attends" a meeting for most of the original Ishiyama delinquents. After the delinquents discuss and conclude on a set plan, they consider who is to be their alliance's leader, until they play a game of rock-paper-scissors to determine who. In the end, due to Baby Beel's participation, he is unanimously made the official "boss".

The following day, Baby Beel and Oga intrude a classroom filled with the Poltergeists from Sōrei High School, including Nasu, even Kanzaki and Furuichi.

Electrocution
When Baby Be'el is caused to cry for one of various reasons, for example Oga being in danger, it fries everything in a certain range depending on how loud he cries. Generally the energy used is higher than that of a 12.000 Volt stun baton Himekawa of the Touhoushinki uses against Oga in chapter 9. Initially, if Beelzebub was more than 15 meters away from Oga, the electric shock would reach a fatal level (for Oga). Due to their new-found trust, this distance has increased by 3 meters. Recently, Be'el has shown the ability to control his lightning and shoot it with enough power to defeat an ordinary demon.

Pee


Once a year Baby Be'el relieves the blessed urine that contains holy demon power. It can't be stopped by simple means such as knotting or diapers and would be able to sink a whole town. This, however was prevented by Oga and Hilda riding on Ak'Baba to the ocean.

Giant Form


In the Demon World, Beel was able to turn into a giant and defeat the monster of the land.

Hidden Potential
While training with Saotome Zenjuro, a radio was used that made a "shadow" of Be'el. This shadow supposedly embodies the potential of its subject, and, as it was able to easily strike Oga into a boulder and crush that boulder, Be'el is hinted to have a large amount of fighting potential.

Later, when Be'el and Oga switch bodies, Oga is seen defeating numerous delinquents using Be'el's body, implying that Be'el already has great fighting prowess but doesn't know how to control his strength.

Super Milk Time


It is revealed by Oga that he is not the only one getting stronger and that Be'el also receives a large power boost when they use Super Milk Time and they also fused after using the "Super Milk Time". At 30 CC, he was able to block the axe of Basilisk, one of the Pillar Heads, and at 80 CC, he was able to shatter the axe. Super Milk Time is a time limited technique.

Super Croquette Time
In the anime, Oga can use Baby Beel's power in turn after Baby Beel eat Croquettes. In reverse, Oga drinks Baby Beel's favorite Demon Milk while Baby Beel eat Croquettes. In this form, Oga synchronize with Baby Beel and took control of his power. He can beat Jabberwock's dragon Sodom without even failing. Oga can use a giant Zebul Emblem to destroy half of Akumano Academy building.

Ankokubutō


Ankokubutō is a technique that allows possession of the body. It is speeding up Be'el's maturation process, as he has his urination period 6 months too early. It also causes him to start teething early. This process might lead to complications later on.

Tatsumi Oga
Oga is Beelzebub's chosen adoptive father, selected both by Alaindelon and Beelzebub himself. Though they get off to a somewhat rocky start, even Hilda is surprised by the strong bond that rapidly develops between Oga and Beelzebub. When not crying or otherwise upset, Beelzebub actually listens to Oga and recalls his lessons on being a man clearly. Likewise, Oga picks up Beelzebub's speech patterns quickly and gets much better at taking care of him. Oga initially only wants to find a stronger parent for Beelzebub in order to get rid of him, but as they grow closer, this search is implied to be more for Beelzebub's own well-being than anything else: he needs a strong, qualified parent to draw out his full demon potential. But Oga already accepted him as his son. Throughout the series, Beelzebub is extremely attached to Oga, prioritizing being with over almost all else.

Hilda
Hilda has been chosen to act as the mother of Beelzebub, and raise him in the human world along with Oga. Beelzebub is close with his wet nurse, Hilda, as shown when she was stabbed by Hecadoth, he cried and even though Oga told him not to cry because Hilda is still watching them, he was still on the verge of crying. He also refused to run away when Hilda told them to run away. Also at the first series, Hilda asked if she should come with Oga to school, Oga refused. That caused Beel to cry and electrify Oga for not letting Hilda come with them. Despite Beelzebub seeming to prefer being with others at times (his refusal to leave Oga for her at the beginning of the series as well as her favoring Aoi while having a switched body) he still cares for her very deeply. He readily calls Hilda his mother, and values her happiness very much.

Aoi Kunieda
Beelzebub is very attracted to Kunieda. When Kunieda displays her strength, Beelzebub was happy. He also seems to be comfortable with Kunieda. When Kunieda was holding him during Oga's fight with Shinjo, he fell asleep in her arms, or when Beelzebub in Oga's body, he smelled demon aura from Kunieda and grasped her twice. Kunieda is also one of the few people capable to hold Beelzebub without him crying. One being Oga, and the other being Hilda. Since Beelzebub is also quite attached to Aoi, Hilda tends to be quite jealous of her.

Trivia

 * In Animax broadcasts, Baby Beel wears diapers over his genitals.
 * Aoi is the only person Baby Beel hasn't shocked whenever he is crying.
 * Baby Beel is currently 2 years and 9 months old.