Hakuei Ren (練 白瑛, Ren Hakuei) is the former Kou Empire's first Imperial Princess. She is also a former General of the Northern Station Corps of the Kou Empire's Western Subjugation Army. Hakuei is the owner of the Djinn Paimon. She is a Dungeon Capturer, having captured one Dungeon, and one of Judar's King Vessels. The soul of the Alma Torran magician Arba, is currently dwelling in her after leaving the body of her mother, Gyokuen Ren and now serves as Sindria Trading Company Top Consultant.
She is a young woman of average height with long, dark hair and blue eyes. She has thin, split-ended eyebrows and a mole on her chin in the same place as her brothers and their mother, Gyokuen. Her head wear has changed from wearing a simple hair ornament on the right side, to a metal headband with horsetail crests framing her face. During her time with the Kouga, she received a scar across her left cheek. After several months, she has acquired more scars throughout her body which describes her brave personality.
She wears traditional feminine robes with lightweight metal armor. She also carries a fan of white feathers which is also her metal vessel.
Hakuei is a kind and determined woman with a strong sense of justice. What she seeks is the establishment of a righteous and united world. For the sake of that noble ideal, Hakuei aims for peaceful world unification propelled by the Kou Empire. Hakuei is a pacifist and aspires for peaceful subjugation through diplomacy rather than conflict. This is because the world she aims for is not one with traces of enmity due to forceful dominion. Contrary to her appearance, Hakuei displays power in being unshaken in her intentions even when about to be slain. She is no naive idealist. Hakuei smiles a lot with almost everyone and remains positive. She is shown to be caring and loving to her comrades, and most especially to her brother Hakuryuu. She'll do what she can do so that she'll make her brother happy by cooking him some of his favourite foods. 
When Hakuei was young, her father and two of the princes, her brothers Hakuyuu and Hakuren, were killed in a fire during a revolt set up by her mother, Gyokuen, though she has only recently learned of this fact. After the revolt, Gyokuen told Hakuei and her only surviving brother, Hakuryuu, that the new Emperor, her uncle Koutoku, will adopt them as his own child and they will still have the title of princess and prince.
Sometime after this, Hakuei was invited by Judar to the Dungeon, Paimon, to get a Metal Vessel. She and her assistant Seisyun Ri captured the Dungeon and she obtained the Djinn, Paimon. After her conquering of the Dungeon, the higher ups of the Kou Empire had a greater opinion of her. They made her the General of the Western Subjugation Army. She and her army were situated near the residents of the Kouga Clan in Tenzan Plateau.
Hakuei Ren first appears when saving Aladdin off an out of control horse. She is with her assistant, Seisyun Ri, and Ryosai. She introduces herself and formally asks the Kouga Clan to become apart of the Kou Empire, but they refuse when Ryosai hits Toya, since she offered horse milk to the Princess. Then, they go away back to Kou Empire's army base. That night, Aladdin goes to visit Hakuei to have a talk with her. She tells him how she doesn't want to invoke war and Aladdin becomes able to trust her. He claimed that the rukh around her were so honest it was almost painful.
Another day, some of the soldiers appear hit by arrows. Ryosai tells Hakuei they were attacked by Kouga Clan's members. Suspicious of what he said, Hakuei and Seisyun Ri go to the Kouga Clan to talk to them, only to be ambushed by the angry clan. They accuse Hakuei's soldiers of attacking Baba, their elderly leader. As she came to understand the situation, she became very angry with her own men and refused to fight the clan, even standing her ground while willing receiving a sword wound to her right side. Baba suddenly appears and, even wounded by an arrow of Kou Empire's army, tells Hakuei that they would join the Empire, much to the dismay of everyone else.
Back at the army base, Hakuei is betrayed by Ryosai, who is revealed to be the cause of the misunderstanding. She is attacked by arrows, but uses the powers of her Djinn, Paimon, to defend herself against it. She starts fighting with Seisyun against the army, but despite her efforts, she is captured since the soldiers were in great numbers. When she is about to be killed by Ryosai, Aladdin appears and uses Ugo to defeat him. As Seisyun wakes up, Hakuei explains how they both captured a Dungeon. Hakuei's Metal Vessel lights up and when Aladdin touches it, it summons a materialized Paimon. Ugo is summoned and they have an unheard conversation, but Paimon explains how she can't help them. Paimon says she only wants to see Hakuei as King and she could care less about the affairs of the world. After talking to Paimon they separate with Hakuei offering to introduce Judar to Aladdin the next time they meet.
She is seen in Hakuryuu's memories of when half of their family were killed.
Hakuei is rushing to the Kou Empire on horses with her Household, Seisyun and over 100 members of the Kouga Clan, behind. In the Imperial City, Koumei is amazed at how quickly she arrived and asks Hakuei who are these people. She explains that as her Djinn, Paimon, seems to be a fertile Djinn, she has so many Household members and thanks to their strength, she was able to fight until now. Koumei states that when it comes to number and the battle power of Household, Hakuei is second to none. Then, Hakuryuu also appears with his Household, creatures created with life magic, Hakuei tells Koumei that they arrived quickly thanks to his help. She seems quite worried about the change in her brother's personality. Then, they enter to the imperial palace and when Kouen arrives shortly after that, Hakuei bows to him.
During the night, Hakuei and Hakuryuu were at the library where Kouen is. She says that Kouen's appearance doesn't quite suit him and he agrees with her, before he turned to Hakuryuu and stated that he wanted to have a talk with him. Kouen then starts talking about King Solomon, who created the Metal Vessels, and the Torran Language. Kouen says that the world will become one, for that reason, a single King must control the world. Then, he asks Hakuryuu and Hakuei to lend their strength to him.
The next morning, Hakuei and her siblings head to the funeral of their uncle and former emperor, Koutoku Ren. She walks into the room and her mother, Gyokuen, greets her children. She is worried when her mother said that the now deceased emperor was sick for quite along time and it suddenly became worse. She is shocked as everyone when Gyokuen, instead of Kouen, became the new Emperor for the Kou Empire; and for the state of affairs if the Imperial Court split into two: one siding with Kouen and the other with her mother. She asks her mother to reconsider taking the throne, but was cut off by Hakuryuu saying that their mother should take it and no one else was suitable. She and her cousin, Kouha, are shocked at this statement by Hakuryuu and the repeated agreement of the persons echoing around the room.
After the funeral, Hakuei goes after Hakuryuu and asks why he did such a thing. He says he obtained the power and now he will protect her. He finally tells her the truth about the death of their father and brothers: was Gyokuen who assassinated them. Hakuei is surprised, but Hakuryuu supposes she already noticed that their mother changed and the group of priests behind her are the Al-Thamen, who are manipulating the Kou Empire. Hakuryuu grabs her hand, saying they will destroy them together and take back their old nation. With a dark expression, he tells her that he lived until today just to realize that. Hakuei is horrified and reminds him what Kouen said one day before: "Division invites destruction", which is why Kouen will not allow an absurd thing such as a civil war; she says the world is one. After the talk, Hakuei asks Hakuryuu if something happened to him and it's not like she doesn't believe him, but now she needs a little time. Then, she apologizes to him.
Hakuei is somewhere with her army, when her cousin, Kouen, calls her and the other Kou Metal Vessel users through long-range Clairvoyance Magic to go to Magnostadt. She answers "Acknowledged" and enters in her Paimon Djinn Equip form.
Aladdin is in trouble because he doesn't have any staff and cannot use his Magic decently when Hakuei uses Paimon's power to catch the Black Djinn and throws them to where the Kou warriors are. Her family destroy the Black Djinn and Hakuei, Kougyoku, Koumei and Kouha appear with Kouen in the center. Aladdin sees Hakuei and calls to her, who is surprised to see him. Hakuei asks Aladdin why is he here but seems happy to have encountered him. Koumei asks her if Aladdin is someone she knows, and that how are they related. Hakuei recalls what happened with the Kouga Clan and Ryosai and, with a smile, answers that Aladdin had saved her life.
Hakuei is fighting against the Black Djinn and says that there's no end to this, and that they have to sever them from the source, that black sphere, the "medium". Alibaba Saluja agrees with her, and says to let's do it. Hakuei uses her power to create a path with wind and wrench the Black Djinn open, so Alibaba can pass through them and attacks the "medium" directly, but fails. A bit after, she and the majority of the Dungeon Capturers are tired. Kouen keeps attacking the Black Djinn alone, and she screams his name when six Black Djinn fusioned attack him. When Kouen digs a hole in the earth with his Agares Djinn Equip, she, astonished, says that he has stimulated the veins of the earth and pulled out a lava flow.
After Kouen has grabbed Alibaba and forced him into a lava flow, Hakuei makes a detailed explanation of what Kouen truly said: that if things continues like this against such a great number of opponents, things will get out of control, so Kouen wants the support of Alibaba after he replenishes his Magoi in the volcano because he controls a flame Djinn just like him. After her more polite and reasonable explanation, Aladdin has doubts about Kouen really saying it. She agrees when Koumei says that they have to protect them so no Black Djinn gets close to them.
Aladdin realizes which is the weak point of the doll and he, Kouha, Kougyoku and Hakuei prepare their attacks, as Koumei will direct them. Hakuei is the first in summoning her Extreme Magic, Pa'ir Al-Hazard, saying "Shatter the Earth! Hear the roar of the Wind God that reduces everything to a cloud of dust...", which has the form of a huge tornado. Kouha and Kougyoku summon their Extreme Magic as well, but their Magoi is insufficient. Kouen and Alibaba join the fight, and after their joint attacks they realize that the doll begins to steal Rukh from the sea and becomes bigger.
The doll suddenly attacks Hakuei, but Aladdin protects her with his Borg. Even so, she runs out of Magoi and loses consciousness.
She fully recovers her Magoi thanks to Scheherazade and summons her Extreme Magic along with all the Dungeon Capturers gathered in the battlefield. She then watches the Medium falling to pieces, hurt and exhausted. Her Djinn Equip wears off and she comes to Kougyoku's side. When the Medium begins to hesitate, Aladdin goes inside it by using Wisdom of Solomon. After his success, she watches the Medium's destruction.
Hakuei and her family are surrounded by the Seven Seas Alliance. When Darius Leoxses suggests that they may be hiding a trump card, Koumei answers him, and he and Hakuei raise their fans. When Sinbad manifests his desire of restore Magnostadt, Hakuei makes an even more angry expression and asks Kouen if can it be that Sinbad calculated that things would come this far and was waiting for the right chance.
An illusion of Hakuei manifests itself inside Belial's dungeon and asks Hakuryuu if what he is doing is just, to which he replies that she was wrong and receives a gash across his left side. As he starts to fall into depravity, Hakuei begs him to return to the right side and fight alongside her, to which he replies by brutally slashing down at her body, killing the illusion.
When the Kou Civil War was beginning to commence, Hakuei was the only King from the Kou nation not to be seen on the battlefield, instead she was protecting the Tenzan mountain range. Her choice to abstain from the war was discussed between Koumei and his subordinate, ending with Koumei ordering him to never utter that Hakuei's actions would "demoralize the army". His last thoughts were him admitting that: "Our emotions are getting in our way, just like hers".
After the two kings Takeruhiko Yamato and Darius Leoxses appeared on the battlefield, Koumei and his men were confused at how they got past the Tenzan mountain range where Hakuei was supposed to be protecting, fearing for her defeat. However, they soon come to learn that she had forged an alliance with the Seven Seas Alliance. On a ship, Sinbad thanks Hakuei for allowing Darius' army for passing through easily, but she does not appear to be pleased with her actions. Even with the look of guilt on her face, she admitted to not knowing any other way to save her little brother's life and said to Sinbad that she was in his hands.
Hakuei has a low amount of Magoi.
Hakuei seems to have been trained in swordplay. She also appears to be very skilled at horseback riding, able to grab the reigns of a running horse and stop it.
Paimon is the Wind Djinn that Hakuei obtained when she conquered the 9th Dungeon. She is the Djinn of Maniacal Love and Chaos. Hakuei's Djinn Metal Vessel is a flabellum with a metal handle, and feather like appendages. Paimon is a fecundity type of Djinn, meaning she is capable of reproducing, which may be the reason Hakuei's Household consists of Seisyun Ri, Dorji, Bator, Boyan, and more than 100 other members of the Kouga Clan.
|“||The Spirit of Maniacal Love and Chaos, I order thine ancestors, To use my Magoi to give me power, Come Out, Paimon!||”|
—Hakuei, Djinn Equipping with Paimon
- Djinn Weapon Equip: When Hakuei equips her Djinn Weapon, she gains her flabellum atop a long rod reminiscent of a Chinese spear
- Magul Al-Hazard: When Hakuei uses this attack, she creates a huge tornado with her in the middle. The tornado starts to spiral and destroys everything in its path.
- Djinn Equip: When Hakuei equips with Paimon, she gains gold, pink and white armor. Hakuei gains the breast ornaments hallmark of Paimon, and . She has a glimmering white dress of feathers and her hair near the face is all made of feathers too. She has a metal headband around her head, and her hair turns to a light color, and is tied into a low tail. She also has a a belt, resembling Kouha and Kouen's one, on her waist. Her Djinn allows her to generate and manipulate small and large windstorms at will to protect her and attack her enemy. These tornadoes are powerful, but because of her lack of Magoi, it doesn't last long. The tornado can be shaped into Paimon.
|“||Shatter the Earth! Hear the roar of the Wind God that reduces everything to a cloud of dust.||”|
—Hakuei's Extreme Magic Chant
- Pa'ir Al-Hazard (Thunder Roar Tornado): When using this Extreme Magic, Hakuei summons an tremendous tornado that can ensnare an opponent in its center and shatters the opponent with it's extreme wind power.
|Quantity of Magoi||
Seisyun is Hakuei’s first attendant, as well as her first household member. He is close to her to the point he is called an "old friend" of hers, a relationship that goes beyond that of servant and master. The bonds between Hakuei and Seisyun is extremely deep, having conquered a dungeon as well as having gone through many trials and tribulations together. Seisyun is the one who makes Hakuei laugh or smile and lifts her hopes up when she's feeling down.
Hakuei loves her little brother and took over the role of their mother after their family was mysteriously murdered. She made sure he could do things on his own, such as cooking. She is used to him worrying over her future and tells him that he shouldn't worry over her. Hakuryuu claims she's the only person he ever opened his heart to.
She is continually startled by his transformation. Since obtaining power, as well as his sudden confession of the truth about their past are things she is still unable to sort her feelings about. In the war between the Kou Empire and Hakuryuu, Koumei's subordinate notes that Hakuei refused to join the fight to recapture the capital, for she did not wish to fight against her little brother. After the execution of Kouen Ren, Hakuei personally thanks Sinbad for supporting Hakuryuu's enthronement. 
Kouen is Hakuei's older step-brother who sympathises with her goals. She endorses Kouen’s ideology of uniting a world that would operate under one ruler. Hakuei admires him, and the two have a fairly good relationship despite the fact that they are step-siblings. Hakuei is one of the few people able to enter Kouen’s private space and seems to understand his quiet but occasionally blunt nature. However, even if Hakuei doesn’t hate Kouen like Hakuryuu, she has mixed feelings since it wasn’t long ago that she was in a higher position than him. Kougyoku once thought why were the both of them seemingly close and Hakuryuu is often infuriated when the two are talking to each other. 
She saves Aladdin from a run away horse during his stay with the Kouga Clan later down he saves her from being killed by Ryosai. She seems to have a friendly relationship with him, even saying as she left for Kou that she should introduce Judar to him next time they meet. When Koumei asks how she and Aladdin know each other, she smiles happily and says that Aladdin saved her life.
- Her name means White Crystal.
- "Hakuei" is the Japanese pronunciation; in Chinese, her name would be Báiyīng.
- Her hobby is sewing.
- Her special skill is equitation.
- She enjoys horse milk and doesn't dislike any food.
- Her favorite type of person is a strong man and she dislikes people who don’t try to talk things out.
- Her favorite way to spend days off is rewarding her subordinates.
- She worries over her lack of skill in sewing.
- Her weakness is cooking.
- Her cooking is at a level that is so bad that it had almost killed her personal attendant, Seisyun, and younger brother, Hakuryuu, many times.
- Though skilled, her catastrophic taste has made her hand embroidered works quite famous.
- According to Morgiana, she has a really nice smell of flowers, similar to Hakuryuu.
- In her early design, she was supposed to be Hakuryuu's younger sister. According to Ohtaka, the story might have been completely different had their relationship been kept like this.
- She is the first to perform a Djinn Equip in the anime, but doesn't actually equip until the Magnostadt Arc in the manga.
- Hakuei is a military commander, and so her entire body is covered in scars (or was).