Seinshun is one of the younger immortals at less than 400 years old. He is also Macallan's great-great-great grandfather. In the 1800's, Seinshun began a separatist movement against the Eden Initiative. He felt that Evangeline had grown drunk with power and no longer embodied the ideals of the Eden Initiative. Her efforts to increase her control over the lives of her fellow immortals led Seinshun to conduct an attack on Evangeline. But the attack failed and Seinshun inadvertently released a virus into Leviathan City, which killed over one-third of the immortal population.

Now, many immortals look to Seinshun as the future of the immortal race. He convinced several hundred immortals to leave the underwater paradise of Leviathan and join him back at the surface of Earth for a life of freedom. But stealth is always a necessity. Retaliation from Evangeline and the possibility of discovery by mortals remains a constant threat. Seinshun is a tactical genius and specializes in being able to hide any evidence that immortals live among humanity. Before he left Leviathan, he raised the Eden Initiative's computer banks for the latest technological breakthroughs and rerouted over $80 billion of the Leviathan fortune to secret rebellion bank accounts in the Cook Islands, Panama and Liechtenstein.

Seinshun is passionate about the rights of all beings, immortal or human, to live in freedom, even if he must sacrifice his own life (or others) to achieve this.