Blue Exorcist is a shounen action series about the son of Satan learning to control his powers in an attempt to rid the world of the demonic forces he was born from. It's an incredibly entertaining series with a surprising amount of emphasis put on developing its characters for a shounen show. The characters draw you in to the story and make you care about what is going on. Let's take a look at these characters and see just what makes them so engaging.
Our main hero of the story is Rin Okumura. Rin is the son of Satan and has inherited his father's power of summoning blue flames. As you might suspect, the Lord of Light is not Father of the Year material and Rin's mother has been MIA since his birth. As such, Rin was raised by an exorcist priest through his adolescence. Throughout his childhood, Rin was picked on and called "demon" and "devil." Rin's powers were hidden from him until he was 15, when Satan attacked the monastery he grew up in. After this, Rin leaves home to attend the prestigious True Cross Academy to train to become an exorcist. Once an exorcist, he hopes to rid the world of Satan for good. He tries to hide his powers from his classmates because what would happen if an exorcist-in-training found out they were working with the son of Satan? Probably wouldn't go over so well.
Rin's body exists in Assiah (the human world) and his flames exist in Gehenna (the demon world). Rin's powers of blue flame are contained within the "Koma Sword" or "Kurikara." This means that while the sword is in its sheath, Rin's powers pose no threat. When it is unsheathed, Rin flares up and exposes his true identity.
The thing that makes Rin such a great lead is that he is a flawed hero. This makes the viewer able to relate to him more and therefore, care more about the story. He is very impulsive and somewhat irresponsible. He gets in fights all the time (both verbal and physical), sleeps in late, and can't keep even keep a part-time service job for more than a day or two.
I think Rin also has a slight inferiority complex when it comes to his brother, Yukio. Yukio always seems to have the upper hand on Rin. He's smarter, more responsible, and constantly receives praise from others. Rin is usually chastised by the some people who applaud Yukio. This leads to Rin always feeling lesser and unworthy, which can in turn cause him to have some rather aggressive outbursts towards his brother.
Despite all his negative qualities however, Rin is still incredibly likable. He has a good heart and is sensitive towards the needs and feelings of others. Although he might act rashly towards them at times, it's clear that Rin really cares about his brother and father. When young Shiemi cries for help, he is the first one to answer.
Rin's heroic traits come from the fact that he is fiercely determined to get rid of Satan. He is willing to fight for his beliefs against all odds. He has a tremendous of ambition and tries his hardest to see that through. He has noble goals and characteristics which make him admirable, as well as likable and easy to relate to.
Not to mention Rin is great at cooking! He is a master chef and has been cooking ever since his childhood. He started out by making omelets that were too salty and still had bits of egg shell in them! He learned to refine his craft and at request of Yukio, began making lunch for both of them. He was also the man in charge of making a birthday cake for all his classmates. He even has a cook off with the Academy's cooking demon, Ukobach, which ultimately ends in a draw.
Yukio Okumura, or Yuki, is Rin's younger brother. Despite also being born from Satan, Yukio does not possess the same power that Rin does. However, he was raised by the same father and in the same monastery that Rin was. He also goes to True Cross Academy to "study" exorcism after Satan attacks the monastery. Yukio actually started training to become an exorcist at the age of seven and was certified at thirteen. When they both arrive at True Cross, Rin finds out that Yukio is not his fellow student, but actually his teacher!
Compared to Rin, Yukio is much more of a "perfect" character and is more in line with a traditional hero in that respect. He is a hyper intellectual and extremely mature for his age. His rational ways of thinking make it so he rarely gets in arguments with people. He never seems to screw up in the same ways that Rin does.
Yukio is also a pretty popular dude. Not only from fellow exorcists who sing his praises, but also with the ladies. Random girls at the academy always make him lunch in an attempt to woo him. Yukio however, much to his brother's dismay, is too stern to be receptive to their advances.
He also never falters in battle. When it comes to fighting demons, Yukio is a master. He has a gun in each hand and a seemingly endless supply of holy water to destroy them. He is never caught off guard and despite the hectic nature of fighting, always remains composed and calm.
That's not to say his character has absolutely no flaws however. He will often quarrel with Rin and say some pretty mean things to him. He calls him useless and wonders why he can't be more responsible.
He also has a tendency to follow orders to a fault. Yukio never questions authority. When he is given an assignment, he completes it as it was intended without second thought. This leads him to make decisions based on questionable ethics later on in the series.
Shiro is Rin and Yukio's adoptive father. He raised both of them since the day they were born. However, he refuses to tell the two of them anything about their mother. He makes up stories about how he came across a giant watermelon and found them inside when he cut it open. Shiro is a loving father and will do anything to protect his boys. When all of the other priests in the monastery told Rin his omelets tasted horrible, Father Fujimoto told him it was a good effort and thanked him for the meal.
Shiro is a renowned exorcist and priest, being the head figure of the monastery. He attained the title of Paladin, meaning he is considered to be the most skilled exorcist in all of Assiah. Despite being older, his skill in combat is also exceptional and makes it easy to see where Yukio inherited that trait from.
Father Fujimoto tries his hardest to keep his sons safe, even though his burden can be overwhelming. Satan continually tries to possess Shiro in order to come back in contact with Rin. Satan wants to do this to try and persuade Rin to ditch his family and come be the demon prince of Gehenna. Shiro is always fighting off Satan's power and does so through keeping himself emotionally stable.
Despite Father Fujimoto's caring nature, he still has shortcomings as a father. After one heated argument with Rin, his emotions get the best of him and he slaps Rin across the face. Although it's an awful thing to see, it actually makes his character seem more like a real person.
Mephisto, also known as Johann Faust, is the director of True Cross Academy. He is a demon who also has the rare ability to shape-shift. He uses this power most often to turn into a talking dog, which he will use as a disguise.
Mephisto is a good friend of Shiro and was appointed by him to be Rin and Yukio's guardian. Mephisto agrees to this because he wants to help raise Rin. He is aware of Rin's powers and sees the potential in him to become the prince of Assiah. He wants Rin develop and control his powers and then use him as a weapon to fight Satan.
Mr. Pheles was also the one who entrapped Rin's powers within the Koma Sword. He did this because he saw the potential danger of Rin discovering his powers too young and because he agreed with Father Fujimoto's decision to raise him as a human being.
One defining characteristic of Mephisto is that he is a trickster. Comparable to the Faustian character from which his name derives or Loki from the Norse legends, Mephisto is a master of deception. You can never believe a word he says, especially when he says it with that sinister smirk. You always know that he is plotting something no one knows about.
He is also the Elder Brother of Amaimon, the Demon King of Earth, who is often used by his brother to do his dirty work. However, Amaimon seems to be totally content with that, which is exploited to no end by Mephisto.
Shiemi is the shy socially anxious daughter of an anti-demon pharmacist. The pharmacy used to be run by her grandmother and is now run by her mother. Shiemi would always help her grandmother with the garden, where the herbs for the medicine are grown. Her grandmother would always tell her the legend of the Garden of Amahara, where every plant in the world grows. One day, Shiemi went to look for the garden with her grandmother's consent. She came home to the tragic sight of her grandmother dead because of an accident. Following this, a demon takes control of the garden and Rin and Yukio come to stop it. This leads to the brothers convincing her to study exorcism with them. She never gives up on trying to find the Garden of Amahara.
Shiemi has a troubled relationship with her mother. She always felt closer with her grandmother because the two would work on the garden together. Her grandmother was also the one who gave her advice when she had problems. Then, when her grandmother died, her mother tried to become closer to her. Shiemi didn't take well to that because she always wanted her mother to be closer to her than she was, and thought her mother was only acting this way now because she had lost her grandmother.
One part of Shiemi's character that is very identifiable is that she feels like an outcast. Being surrounded by only her family members, she never felt that she had any friends before enrolling at the Academy. Friendship is something she desperately desires, her social anxiety just prohibits her from trying to interact with others. It leads to her basically acting like Izumo's servant for a brief time because she wanted to be friends with her so badly. Eventually, she does learn to make friends with her classmates which is rewarding for both the character and the viewer.
Some exorcists are able to summon "Familiars," or demons which they are spiritually tied to. Shiemi has the ability to summon the coolest demon in the show, the Infant Greenman. The Infant Greenman is an adorable body made from plants who has the ability to grow any plant in existence at Shiemi's command.
Among Rin's classmates, Suguro (also referred to as Bon) is his rival. Suguro grew up in a temple as the son of its head priest. He is a rare survivor of an event known as Blue Night. During Blue Night, Satan murdered not only all the priests in Suguro's temple, but all of the most prominent clergymen in Assiah and their families. After the temple was destroyed, Suguro was berated by townspeople for being cursed. All of these factors contributed to Suguro realizing his life's goal. Destroying Satan.
Not only do Bon and Rin share the same goal, but they also have the same dedication and ambition to see it realized. His determination to defeat Satan leads Suguro to excel in all his classes and be skilled and knowledgeable when it comes to the study of exorcism. He is also athletic which contributes to his skill in fighting.
Despite their similarities, Rin and Suguro butt heads more often than they get along. Suguro gets angry at Rin for falling asleep in class and doing poor on tests because he thinks it means Rin isn't serious about becoming an exorcist. Their rivalry eventually leads to the two of them competing against each other in their physical education class. They are being chased by giant demon frogs (I know, awesome right?) known as Reapers, and are trying to outrun each other in the process. The race eventually ends and Rin reveals his goal. Suguro proceeds to claim that Rin "copied" him by having the same goal of fighting Satan. Rin then tries to prove him wrong and a huge argument breaks out.
To put it plainly, Izumo does not play well with others. She is a student at True Cross Academy and is one of the most powerful and adept soon to be exorcists in the school. She harnesses great potential which is seen by all the higher ranking exorcists.
However, her cynical personality causes her to have some issues at the Academy. She is mean to everybody except her one close friend, Paku. She befriended Paku when she was younger because Paku was the only one who didn't immediately dismiss her because of her nasty demeanor. Her bad attitude manifests itself most notably towards Shiemi. After Shiemi extends an invitation of friendship, she pretends to be her friend only so she can have Shiemi buy her things and carry her bags for her.
This side of her personality often does not work out to her advantage. Once when Paku was being attacked by a demon, she tried to help her friend by calling her Familiars, two white foxes. Her foxes turned to her and told her that she was not worthy of them and vanished. Rin and Shiemi had to come in to save Paku.
Izumo does have a soft side however, one that she tries to hide. She puts on a tough exterior so her sensitivity won't show. When Paku was being attacked by the demon, she started to cry because she realized that she couldn't help her friend. Afterward, she washed Rin's clothes for him and told him to keep it a secret that he saw her cry. The fact that she wasn't able to help Paku leads her to think that there is something wrong with her because she can't help the way she acts.
Shura is a first-class exorcist and disciple of Father Fujimoto. She was assigned by him to look after Rin and to properly train him in the use of his Koma Sword. She has great admiration for her mentor and looks up to him as a surrogate father figure.
For the first half of the series, Shura is one of Rin's classmates at the Academy. She always wears a hood over her head so nobody can see her face. It is also rare for her to contribute anything to a conversation, instead preferring to play her golden PSP. Finally, she reveals to Rin who she is and tells him that she was in disguise because she was given orders to work as an inspector watching him. After she tells everybody who she is, she becomes an instructor of the class.
Her orders to work as an inspector were given to her by the Vatican, who all exorcists answer to. Her orders were actually to kill Rin if she found out that he was related to Satan. However, she goes against the Vatican's wishes because she doesn't want to let her mentor down.
Shura is an incredibly skilled swords-woman. She draws her sword out of a summoning circle (which bears an uncanny resemblance to the transmutation circles from Fullmetal Alchemist) on her chest. She has the ability to change the shape of her sword to one resembling a snake. When this is done, the sword curves out at the end and grows an eyeball.
An amusing part of Shura is that she likes to drink. She has a particular fondness for beer (we have something in common!) This is apparent when her and the rest of the class are out in the forest and she becomes visibly inebriated while the rest are out on a mission.