Tatsumi Oga is the main protagonist of the Beelzebub anime and manga.
Tatsumi is a young delinquent and first year at Ishiyama High, the delinquent school. At the start of the series he already holds quite a reputation, being known as "Rampaging Ogre" or the "Strongest Juvenile Delinquent". The story starts as he is telling his best friend Furuichi of how he first found Baby Beel. One day whilst fishing (actually, taking revenge on some gangsters who tried to kill him in his sleep), he sees a dead man floating down the river, pulls him to shore and the man splits in half revealing a baby boy. This boy is the son of the demon king and Oga soon finds he has been chosen as the one to raise it, along with the baby's maid Hilda. The story follows his life as Baby Beel's father, and the events at Ishiyama as he battles for the title of the strongest.
Oga was picked to become Beelzebub's father because he possessed the qualities of the ideal parent for the future Devil King: strength, arrogance, and a think-nothing-of-fellow-man outlook. Despite this, Oga isn't completely evil: he only really bullies those stupid enough to attack him in the first place and is willing to stick his neck for his True Companions without a second thought. He also takes time to teach Baby Beel what it means to be a "real man" (when he's not trying to get rid of him that is). He easily gives in to flattery and is an avid Dragon Quest fan.
In the AWA fics, Oga is a student at the AWA Academy and is part of Class 2.
In the XP4 fics, Oga debuted in the XP4 Heroes Coalition - Remnant Chronicles.
Oga is usually seen sporting a grotesque grin and displays demonic features when he is either angry or disturbed. He possesses brown hair and sharp black eyes, he is rather muscular with a widespread build, and his attire usually consists of a worn-out shirt, his brown leather jacket, and plain pants (usually jeans). He has been shown on a few occasions to be wearing either sweatpants, and on one occasion, has even been shown wearing his pajamas (ironically very detailed with pinstripes going down the side). When Oga attempts to smile, he is usually seen with a demonic, evil grin. This speaks to his lack of social skills (due to his inhibition in a juvenile delinquent high school). When fighting, Oga appears to have a different look. Aside from his rare comedic entrances (usually as a relief from an intense situation), he is usually very calm and actually quite aware. His eyes are alert and he seems in control of his emotions. Beel does not transfer this emotion, however, and is usually shown in a maintained and alert state.
When he uses Super Milk Time, he becomes one with Baby Beel. His hair is green and he is sucking the pacifier Baby Beel uses. He is the same height that he is in his original state, and wears the same clothes.
Initially, Oga was nothing more than a crude and uncaring delinquent whose only friend seemed to be Furuichi. While he wouldn't start fights, he would take deliberate pleasure in inflicting the most pain possible when facing his opponents, regularly resulting to cruel and unusual methods of punishment for his defeated enemies, showing a high amount of sadism. It is because of these qualities that he was initially chosen to become Beel's parent. Alaindelon described the ideal parent of a Demon Lord as being "strong, tough, self-centered, and cares nothing for his fellow man". These traits sum up most of Oga's personality. As the series continues, it should be noted that the trials Oga has faced and the new friends he has gained have somewhat altered his personality. For example, when the Rokkisei called out Ishiyama to meet them on the rooftop, he initially came alone. But later on when Himekawa, Kunieda, and Natsume arrived, Oga smiled, knowing that they have his back. Though he retains his love for his cruelty, he is now much more calm and easier to be around than he was at the start of the series. Still, in his own twisted, roundabout way, he seems to care for the people that are close to him. When Furuichi was gone during the summer vacation and left Oga alone, he called Alaindelon to transport Furuichi back home just so he could hang out with him. He also beat up and embarrassed Miki back in middle school, though he did it to protect him from Kiriya Reiji. Since he knew that both Miki and Kiriya would move to Nara at the same time, Kiriya would've attacked Miki in Nara where Oga wouldn't be there to protect him. When Hilda and Beel went missing and his sister Misaki threw him out of the house, promising to not let him back in unless he brought them back, Oga acted as if he didn't care. Instead he complained about the heat to Furuichi and decided that they should go down to the river. Furuichi realized that the river was where Oga had first met Beel, also realizing that Oga meant to look for them after all.
Oga doesn't seem to have any sense of appeal for or opposition against girls, unlike Furuichi, who is easily seduced and will not hesitate to pick up girls. However, he does also has a sense of chivalry, as said by Hilda, as Oga will not fight or harm a woman. This was proven true when he only dodges during his fight with Aoi, and more recently when fighting the female Pillars he held back when he realized he was about to hit a girl. The only times he actually hits a girl was during a sparring match with Aoi to determine if they were capable of learning Black Techs, and knocking out Yuchelle by destroying her weapon. It is also hinted that he disapproves of underage smoking and drinking.
As much as Oga hates it, he tends to listens to lectures very well. For example, when Oga was telling Teimō about Baby Beel's demon praying dance, Kunieda quickly takes him to the side and lectures him about being selective about who to talk to about Demons, and to only talk about them to those who are involved. After that, Oga never told anyone besides Furuichi, Kunieda, Ittōsai, and Saotome, save for other demons. Another example of Oga paying attention is when Saotome was lecturing him about using Super Milk Time for no more than 5 minutes. When he uses Super Milk Time later, he only ended up fighting for 5 minutes after using a huge blast that knocked him unconscious.
As the series progresses, Oga learns how to put his pride aside and knows when to follow orders. An example was when Saotome said that the Ishiyama students were going to need training with him. All of the delinquents didn't want to train with him because they thought he was an "old geezer", and that he was weaker than them and it would damage their pride. Oga was the only one who stepped up and agreed to train; instead of being arrogant, he listened to reason and sought to become stronger.
Tatsumi is a member of the Heroes Coalitions and is part of the Triumph Division. He also attends Vanguard Academy as a student.
XP4 Heroes Coalition - Remnant Chronicles
In Chapter 3, Tatsumi, alongside Baby Bel, Ike, Rey Dynamic and Prince Mufasa arrives at the house yard somewhere in Mistral as additional help, much Eijiro Kirishima, Jaune Arc, Lie Ren, Nora Valkyrie, Mina Majikina, Brook, Oscar Pine/Ozpin and Ruby Rose's awe.
Expert Hand-to-Hand Combatant: Oga, even before meeting Baby Beel, has only used unarmed combat to fight. He uses street brawling and his already inhuman strength to win fights. Now that Beelzebub is with him his strength has been further enhanced with demonic energy. Oga likes to make up crazy names for his attacks even though they're still only regular moves. As with most thugs in the series, he lacks any particular martial art technique in fighting, mostly relying on his natural prowess to diminish the advantage of trained martial artists like Kunieda and Miki. However, he has figured out some classical techniques from wrestling: he outmanuevered and defeated Tōjō with a German Suplex and leads Baby Beel to do a Clothesline, an Elbow drop, and a Boston Crab to defeat the huge monster they encountered in the Demon World. He is able to hold his own against a Demon for some time without resorting to use Demonic power (although he did use the Zebub Blast against this enemy, it had no effect). He can feel Saotome using his demon power, which shows he has notable strength for a human.
- Street Fighter Techniques:
- Psycho Crusher (regular punch)
- Shouryuuken (regular punch)
- Yoga Chop
- Rocket Punch (regular punch)
- Flash Kick
- Finishing Moves:
- Super Rocket Punch (regular punch)
- Infinity Rocket Punch (regular punch)
- Maou Rocket Punch (regular punch)
- Oga Special Punch (regular punch)
- Demon Punch (regular punch)
Martial Artist: Later, though, upon having to be rescued from a confrontation with a demon by Saotome, he becomes irritated by the fact he is unable to protect anyone and decides to take formal training from Kunieda's grandfather. Oga trained in the Shingetsu style with Kunieda and Kunieda's Grandfather. He showed himself able to learn at a fast pace, splitting stones and even boulders bigger than himself with the Shingetsu's style basic technique: Nadeshiko.
- Nadeshiko: Nadeshiko is a technique were the user focus his or her power completely on a single spot. This technique is also known as the Armorpiercer.
Weapons Specialist: Though he prefers to use his bare fists, he is also very proficient in use of weaponry, such as crossbows and short swords (used when storming Akumano High to great effect against demons)
Spell Master: Originally because of both Oga's inexperience with demon powers and his obsessive search for another parent for Baby Beel, Oga possessed little to no abilities with utilizing a demon's power. He would first display this capability by instinctively using beel's power in a basic maneuver by channeling the demonic energy and releasing it in an energy blast. After being resuced by Saotome, Oga reluctantly trained under him in the demon arts and after a week the delinquent would expertly use the same technique that Saotome used to drive the Pillar Division demons away. After the arrival of the entire 34th Pillar Division, Oga would trained under Suiten Ikaruga in Black Techs to utilize Beel's demon powers. After this training Oga became able to easily defeat a Pillar Baron with one move when previously he needed to merge with Beel to defeat a Pillar Baron. Also Oga displayed better fighting ability against Jabberwock when he previously could do nothing against the general and narrowly defeated the demon. In time Oga subconsciously developed a fatherly relationship with Beel that in turn increased their bond and shared power which is noted by many characters including experienced spell masters that allowed him defeat the spell masters while his skills remained underdeveloped. Eventually when his and Beel's relationship is fully developed, Oga was able to fully release Beel's latent powers that allowed him to dominate against a spell master who had merged with a member of the Seven Deadly Sins and had also merged the powers of those who follow him together.
- Oga along with Baby Bel are the first characters from Beelzebub to be introduced in the AWA fics.
- The first part of his first name, Tatsu, means Dragon. This is a play on the Eastern mythology of the Tiger and the Dragon, in which Oga is the Dragon and Hidetora Tōjō (Tora) is the Tiger.
- When Oga switched bodies with Beel, he stated that he wanted to play the piano.
- Oga's perfect impression of himself is like a boy in a shōjo manga while holding a glass of wine.
- Along with Baby Bel, Tatsumi are the first characters from Beelzebub to appear in the Heroes Coalition fics.
- In the Heroes Coalition, Tatsumi has high-respects for King Forest for some unknown reason.