As a child Drei dreamed of becoming one of the Ten Sages and worked hard in order to receive the title. At some point, Zwei became his mentor and he looked up to her as a member of the Ten Sages with merit. However, she disappeared six years before the events of XBlaze Code: Embryo, crushing his opinion of her. Once Sechs became one of the Ten Sages, Drei became enamored with him for his talent and decided to follow him no matter what.
Code: Embryo, Lost: Memories
In Ishana, Sechs, Drei and Acht met to being their plan. Drei told Sechs that only he embodied the attributes of a true Ten Sage, living honorably and using their power to lead other towards the truth, and he wanted to follow Sechs to see his plan come to fruition. Sechs said that it was pointless of Drei to ask for permission if he had already made up his mind. Drei apologized, knowing that Sechs hated wasting time and said he would follow Sechs of his own free will, promising to tear apart anyone who would stand in their way. Acht called him pathetic and Drei asked why she chose to follow Sechs but she refused to answer. Drei said he would not accept if Acht did not take this seriously but Acht replied that she was determined, revealing that she voluntarily became a Union. This proved her determination to Drei, who said he needed to rethink his opinion of Acht. Acht asked if he wanted to become a Union as well but Drei said that since he wanted to see Sechs's world with his own eyes he couldn't afford to take risks so early on.
After stealing the Kusanagi, Sechs told Acht that his father was an unworthy vessel. Acht was shocked that Sechs used his Drive and Sechs said he used it because Lord Stroheim desired power. Drei arrived, telling them that preparations for their escape were complete and they would be heading to Shin Yokozaki City. 
In their hideout, Drei and Acht were present while Sechs watched the encounter between Akira Kamewari, Kuon Glamred Stroheim and Akio Osafune through a mysterious crystal. Drei noted that the Grimoire was present. 
That night, he arrived to stop Touya Kagari, Es and Kuon from interrogating Akio. He refused Kuon's demand that he return to Ishana and, when she reveals that she had been given Sealed Spear: Izayoi, warned her that using it will have dire consequences. He told Kuon to return to Ishana so that Kuon's mother won't lose both her husband and daughter. Once Acht arrived and started stepping on Akio he told her she's overdoing it and picked up Akio. The two then departed. 
After recovering Akio, Drei saw that his crystal has progressed to phase five and claimed he was useless. Suddenly, Ripper appeared and killed Akio. Drei wondered how Ripper could break through his barrier but Ripper said it was easy. Drei then asked Ripper to help unleash the Grimoire in exchange for a crystal but Ripper said he could get those on his own. Ripper wondered if it would be interesting and demanded to speak to Drei's boss instead of him. Drei got angry but Sechs arrived. 
The evening after Akira removes his crystal, Drei, Sechs and Acht approached Touya and Souichiro Unomaru, since Sechs wanted to talk to Touya. When Touya asked why they made Akira into a Union, Drei said that Akira did it of his own free will. Acht said she had no more use for Akira but she'd gladly kill Touya if he wanted. Drei told her to stop since Touya is important and she sarcastically said she'd be a good girl. After Sechs told Touya to ask himself why he exists, he disappeared alongside Drei and Acht. 
Once Touya awakened the power of the Origin of the Grimoire, Drei and Sechs appeared before Kuon and Mei Amanohokosaka. Sechs told them that they needed the power of the Black Beast to destroy the Embryo. Drei told them that Unomaru was planning on using the Embryo to control the minds of everyone in the world. He warned Kuon and Mei not to get in their way or they would return them to seithr and that all that mattered was the future Sechs is trying to create. Sechs and Drei then disappeared.
Later, he attacked Touya and Es in the sewers. Es blocked the attack from hitting Touya and Drei said his aim was off since he was aiming for Es, calling her a “doll.” Touya angrily claimed that Es was no different from a normal human but Drei said that artificial beings are not part of Sechs's plan and therefore cannot exist.  Drei attacked Es but Touya took the attack for himself. Drei told Touya to stand aside and watch him kill Es, attacking her again. As Touya started to lose control he told Es to fulfil their promise but Drei stopped Es from killing him. Touya then unleashed the power of the Origin of the Grimoire on him. When Touya refused to back down, Drei said that he could still break every bone in Touya's body, as long as he didn't kill him. Touya threatened to unleash the Grimoire again but nothing happened. As Drei was about to attack he was stopped by Avenge. Drei was confident that a bounty hunter wouldn't be able to stand up to one of the Ten Sages but Avenge was able to dodge his attacks. After Touya and Es ran off, Drei said he would deal with Avenge first at his leisure. Drei asked Avenge why he was attacking him even though Avenge only hunted down Unions, which Drei was not. Avenge was angry that the Magic Guild lied to him but Drei said it didn't change anything, and he would kill anyone who got in Sechs's way, calling Sechs the only “true” member of the Ten Sages. Avenge asked Drei why he was so obsessed with the Ten Sages and Drei says it's because he's dreamed of being one since he was a child but the title didn't have the meaning it was supposed to and even his mentor Zwei abandoned the Magic Guild six years ago. Drei was devastated that who he felt was the only worthy member of the Ten Sages left until he met Sechs, who became a member of the Ten Sages through his skill despite his families prestige. Drei then prepared to attack Avenge.
After the battle, an injured Drei was collapsed against a wall. He was unable to use healing magic on the wounds created by Avenge's knives. He was then approached by Zwei. Drei initially assumed she was an illusion, but she insisted she was real. Drei wanted to know what Zwei was doing in a place like this and she said it's because the truth exists in places like this. Drei assumed she was talking about the Azure but Zwei insisted she had no interest in it; that being able to know and do everything is boring and life is only interesting if you discover things for yourself. Drei said that she was always so free from the rules of the Ten Sages while Zwei counters that he was too bound by them. Drei said he wished he could have been more like Zwei before dying. Zwei decided to send him off, disintegrating his body with her Azure Requiem spell and praying that his soul will find peace. 
- XBlaze Lost: Memories, Additional Scenario: Sechs
- XBlaze Code: Embryo, Episode 2
- XBlaze Code: Embryo, Episode 3
- XBlaze Code: Embryo, Episode 4
- XBlaze Code: Embryo, Es & Hinata Route Episode 8
- XBlaze Code: Embryo, Es & Hinata Route Episode 9
- XBlaze Code: Embryo, Es Route Episode 10