Also known as: 怪盗X, 怪盗サイ, Phantom_Thief_Sai, X_(Neuro)
An antagonist in Majin Tantei Nougami Neuro that goes by "X" (pronounced "Sai"), and known as "Kaitou Sai" (meaning "Phantom Thief Sai").
This character was born female, but uses male pronouns and has the ability to transform into multiple forms including initially that of a young boy with silver hair, later they are seen in their original true form as a girl with long Black Hair. They are an altered Clone of Sicks (Neuro).