He is a member of the Dandelions and was chosen by the Master of Masters to lead a Union after the Keyblade War. Like the other new Union leaders, he was given a book with laws set by Master Ava.

After the final Union leader, Lauriam, arrives, the Union leaders go to Daybreak Town and enter the Foretellers' Chamber, where Brain finds a copy of the Book of Prophecies and starts flipping through it. When Skuld proposes that they begin choosing which Union each of them will lead, Ephemer recommends that they maintain the Union χ in order to prevent the conflicts of the past world, with the other Union leaders agreeing to reconstitute the old system later as stated in the rules. Brain then suggests that, while the Dandelions are reliving the events of the past, they collect the necessary ingredients to create new Spirits and sends Ephemer, Skuld, and Ventus to collect the ingredients while he and Lauriam stay behind to make the necessary preparations.

Brain has black spiky hair that droops down over his eye. He wears a black coat with rolled up sleeves, gold buttons, and a large collar, grey pants, and black cowboy boots. His face is concealed by a black fedora that sports a black feather with a tan streak down the middle.