Siyun is a well-built man with white hair and light blue eyes. He is always seen wearing casual or simple. When he first became an idol, his hair was black. He then later dyed it to white

In his regular form Curtis has the upper body of a human man and the lower body (tail) of red snake, like a Lamia, his human part is tall, slender and muscular with long silky, straight red hair and matching eyes. As a Beastman he has a full animal form too, that being a large red snake. He can willingly shift between each of these forms. His Beastman marks are displayed on his torso and neck.