Sean Lacich, once a regular teen, dies in a building collapse. A Anodite Celestialsapian hybrid decides that she'd like to split his soul in two and have both halves reincarnate in two different bodies, children from the Gremory and Phenex familys.

One half of the soul was reborn as the first born child of Sirzech and Grayfia, but was not born as a Devil, still human, because his soul was not corrupted like most human souls that became new born Devils.

The same occurred with the other half of the soul, but born from the Phenex Family, the eventual middle child, after Ravel is Born.

Both familys were forced to give up the children, the only ones who were saddened were Sirzech, Grayfia, and Lady Phenex. The rest of the Gremory family never knew of the child.

Little did any of them know, the two children inherited their familys blood trademarks, the Power of Destruction, and the Phenex fire.

The Two halves eventually met, and MERGED, becoming one being, the soul still partially split. They could split apart safely, but they could remember their entire previous life when they were one, they were two halves of one whole, which reminded them of Kamen rider W, which apparently exists in their current world.

The halve born of Gremory named himself Seich(Pronounced Switch) Halve Patrimory, honoring both half his name from his previous life and the last name of the family he was born from.

The Halve born of Phenex named himself Lacan(Lacken) Halve Phenrick, honoring the other half of his original name and part of his birth family's name.

Together they were Sean "W"(double) Grenex. When whole, he had the blonde hair of Phenex on his left, and the red hair of Gremory on his right, his eyes are Hazel like his previous incarnation.

He could not become a devil, not because he didnt want to, but because it was impossible for him to.

He one day encounters Kuroka, full aware of who and what she is, as well as the truth. He encountered her while she was being chased by a entire peerage, he had been Sean "W" when this happened, so he jumped in and beat them all down, but didnt kill any of them, and when the king asked just who he was, he said, "I'm the Two-in-One Destructive Pheonix", before he knocked Kuroka out and fled.

His ability are found out when his is able to participate in the rating game with Riser, the brother that wanted him dead for simply being born human. He splits so they can make an epic entrance moments before fighting Riser, revealing that he truly is two-in-one, and uses both his powers against Riser, obliterating him in minutes, winning the game for Rias, his Aunt that didnt know he existed. He quickly opens a portal to leave to avoid questioning, but not without saying, "Sayonara, Aunt Rias, tell Riser his younger Brother forgives him for wishing his death".

Sona had her suspicions about Sean "W", investigating everything she could, learning he was connected to Seich and Lacan, to how he mysteriously appeared at an orphanage at the same time as Seich and Lacan disappeared. She even extended her search for answers by watching Kamen rider W, and ended up getting hooked on Kamen rider in the process. When she saw two Teens that resembled Seich and Lacan, merge into Sean "W" she instantly made the connections she been wanting, but then he is suddenly able to use The power of Destruction and has the Phenex fire and healing. But suddenly Rias relays the last thing he said to her,"Sayonara Aunt Rias, Tell Riser his Younger Brother forgives him to wishing his death". She was suddenly able to make every last connection, Seich had a last name related to Gremory, and Lacan had one related to Phenex, and Sean "W" has one related to both. Somehow he was related to both clans.

Soon Gabriel and Michael arrive, putting everyone on edge, but they explain they knew of Seich and Lacan, and but default Sean "W"s, origins. Revealing some being from another universe had split a soul in half and had both halves reborn into the familys of two high ranking devil clans, but they were born human, having been killed saving people in a collapsing building, overwriting his sins, meaning he couldnt be born as a devil as he was now an anomaly in the reincarnation system. They went on to explain that the halves eventually met and found out how they were once one person in their previous life. Its soon found out that Ravel and Millicus had left to meet the person that was both of their older brother.