Hakuryuu Ren (練れん 白はく龍りゅう, Ren Hakuryū) is the fourth prince of the Kou Empire, and later the fourth emperor following his vengeance on his mother Gyokuen Ren. He is also a Dungeon Capturer, having conquered Zagan and Belial. Initially, Hakuryuu pledged allegiance to the Seven Seas Alliance, but later defected before abdicting the throne to Gyokuen Ren, and becoming one of the world's three most wanted criminals.
Hakuryuu is a young man of average height and build. He has dark blue hair and blue eyes, the left eye being a paler shade than the right. He has a large burn scar on the left side of his face and body which he received when he was a child. He also has thin, split-ended eyebrows and a mole on his chin, in the same place as his siblings and their mother, Gyokuen. He wears traditional clothes typical of the imperial royalty of Kou. He always carries a halberd, which later becomes his Metal Vessel of Zagan.
Originally, Hakuryuu had real flesh limbs, but had lost his left arm to Ithnan and later both legs to Alibaba Saluja. To compensate for these losses, Hakuryuu used Zagan's power to create prosthetic wooden left arm and legs. Ultimately, Hakuryuu returned to have flesh limbs again thanks to Kouen Ren, who gave his own limbs to Hakuryuu with the power of Phenex.
He has a serious personality and is concerned about small things. He also has a bit of an inferiority complex. Due to this complex, he becomes quite pessimistic whenever people surrounding him notice his weaknesses and takes such criticism personally.
It is revealed that he harbors an intense hatred for his mother, due to her secretly murdering half of his family. After he remembers this, Hakuryuu becomes obsessed with seeking revenge against Gyokuen for her deeds. He now mercilessly slaughters his enemies, as seen when he beheads Umm Madaura in front of her "children", and when he ****s all of Hakuei's enemies on the Tenzan Plateau. He wishes to tear down the current Kou Empire and replace it with the former one, one that isn't controlled by Al-Thamen. He believes that hatred can never be erased, and the only thing you can do is erase the ones you hate. He eventually fell into depravity and sought to eliminate all that stand in his way. However, after having a talk with his defeated brother, Kouen Ren, regarding Arba's immortality and ability to change bo****s, along with words from Aladdin and Morgiana, he came back from depravity after concluding that his justice (which once advocated annihilation) had changed, with Kouen's **** execution and exile being proof of that.
As of the Final Arc, Hakuryuu has fully given up on revenge despite discovering Arba possessing his sister's body and charging in angrily at Arba (the latter being a ruse to get information). With revenge out of his psyche, Hakuryuu is much more sane and in control of himself.
Hakuryuu has a very troubled past. When he was six-years-old, he was caught in a large fire during a revolt, and tried to flee with his brothers, Hakuyuu and Hakuren. While they were ****ing Al-Thamen members left and right, Hakuyuu said that he can neither **** nor let them have their way, and Hakuryuu wonders if their mother, Gyokuen, and sister, Hakuei, are alright, and if they should go help them. His brothers look at him then decide to keep going.[3]
Eventually Hakuren ****d and Hakuryuu was left next to a badly burned Hakuyuu, while crying for his mother. Hakuyuu said that unfortunately it was the end for him and Hakuren, but that Hakuryuu will live and accomplish their mission. Hakuyuu told Hakuryuu to swear to fight to the very last and that he has to strike down the Kou Empire's worst enemy. Hakuryuu asked what he was talking about, and why the sol****rs of Kou wanted to **** them, and who would do such a cruel thing. Hakuyuu revealed the name of the perpetrator, but Hakuryuu didn't believe him. To save his brother's life, Hakuyuu stabbed himself, drenching Hakuryuu with his blood, and ordered
