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 some by 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 polearm, which later becomes his Metal Vessel of Zagan. He has a prosthetic wooden arm, attained via Zagan's power, having lost his left arm to Ithnan.
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.
He greatly treasures his sister, Hakuei Ren, who has not only become a mother figure for him but is also the last of his siblings.
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 kills 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.
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 killing Al-Thamen members left and right, Hakuyuu said that he can neither die 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.
Eventually Hakuren died 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 soldiers of Kou wanted to kill 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 him to go before the fire reached him. The incident still caused him to receive the burn scar on the left side of his face, and some on his body.
After the revolt, Gyokuen told Hakuryuu and Hakuei that the new Emperor, their uncle, Koutoku Ren, would adopt them and they would still hold the title of prince and princess, although Hakuryuu would rank below Koutoku's sons. Soon after, Hakuryuu, not believing what his brother had said, asked his mother for the truth. She admitted it and said that she will marry the new Emperor. Later, Hakuei asked him what was wrong and he lied, hiding the truth about their mother, believing he had to protect her.