He is the top designer of Futuring Girl, Aoi's favorite brand. He wanted to make a prefect dress but because of all the pressure he put onto himself, he never realized it was perfect the way it was. Rei locked himself in a shell until Aoi told him that it wasn't all about perfection. As thanks, he gave Aoi the premium cards, the Kaleido Mirror Coord.

(Source: Aikatsu! Wikia)