Azure Heir's real-life appearance is described by Takanouchi Koto to be attractive in a very Japanese way, with his hair styled in a bowl-cut fashion. At the time, he was wearing a navy blazer and ivory pants.
Azure Heir is a kind Burst Linker who is rather naïve. He helps Silver Crow and Ardor Maiden escape when they are trapped within the Imperial Palace. His manner of speech is that of the feudal lords of Japan.
He first showed himself in front of Silver Crow and Ardor Maiden within the inner sanctum of the Imperial Palace. He introduced himself as Trilead Tetraoxide and guided them during their stay. To the surprise of Haruyuki and Utai, Azure Heir was in the opposite situation as the vast majority of Burst Linkers. While most Burst Linkers were locked outside of the Castle, trying to find a way inside, Azure Heir was locked inside of the Castle, trying to find a way outside.
When they were ready to escape, Azure Heir used The Infinity to force open the gate leading outside, thanking Haruyuki and Utai for meeting him before closing the gates once again.
In Volume 18, it revealed his parent is Graphite Edge. He introduced his parent to Haruyuki when he entered the Imperial Palace the second time alongside Sky Raker and Metatron. After Haruyuki's second intrusion into the Castle, Azure Heir also escaped alongside him.
Shortly before the attack on Oscillatory Universe in Volume 20, Azure Heir met with Haruyuki and Kuroyukihime in the Unlimited Neutral Field to officially become a member of Nega Nebulus. Coincidentally, he had dived in the same cafe as Cobalt Blade and Manganese Blade of Leonids, the blue legion. Suspecting that the real-life persona of Azure Heir was a spy from the White Legion, the Dualis followed him into the Unlimited Neutral Field. There, they realized that it had all been a big misunderstanding. In the short conversation afterwards, the two sisters were extremely impressed by Azure Heir's weapon, The Infinity.
In Volume 21, during the attack on Oscillatory Universe during the Territories that same day, Azure Heir was spared from the Infinite PK trap set by the White Legion. After Silver Crow and Lime Bell escaped from the trap and were subsequently attacked by Shadow Cloaker of Oscillatory Universe, Azure Heir saved both of them, killing Shadow Cloaker in the process. Afterwards, he assisted Silver Crow and Lime Bell in recovering the true form of Metatron, as well as in the fight against Rose Milady of the White Legion. Finally, he sacrificed himself in the process of transporting Lime Bell to the location of the other Nega Nebulus members in order to dissolve the White Legion trap.
Trilead's net avatar is modelled after nobles in the Heian period. He wears azure nōshi robes and a black eboshi hat, as well as a porcelain mask.
Azure Heir is modelled after a feudal daimyo, looking like a "young samurai". As its name suggests, he is a highly saturated blue, which suggests that he specializes in close-ranged combat.
- The Infinity – The fifth of the Seven Arcs, represented by Epsilon Ursae Majoris, also known as Alioth. It takes the form of a straight sword resembling a katana. It possesses an innate ability that allows the power of its first attack to grow the longer it stays in its sheath. As its name suggests, the power of this initial attack can grow without bound.
- Heavenly Stratus – This Incarnate technique used by Azure Heir is likely a second-stage Incarnate technique that combines Range Expansion and Attack Enhancement. Heavenly Stratus consists of a horizontal sword slash from left to right, immediately followed by a vertical slash from top to bottom, drawing out a large "X" shape that then flies forward. When used in combination with the straight-sword the Infinity, Heavenly Stratus contains enough attack power to break the seals on the Castle gates.
- Genuine Specular – Genuine Specular is a defensive-type Incarnate technique used by Azure Heir. When used, the Infinity will be brandished horizontally, turning into a large mirror shield. This ability is used by Azure Heir to mainly defend himself and his comrades. While Heavenly Stratus provides attack power, Genuine Specular provides defensive ability.
- Blast Wave – One of Trilead Tetroxide's Incarnate abilities. Using the Infinity, Lead can launch a crescent-shaped shock wave as an attack.
- His real life identity is speculated to be the Imperial Prince of Japan.
- The name that he first identifies himself as, Trilead Tetroxide, is a chemical compound by the formula of .