Mitsuhide Nira (仁良 光秀 Nira Mitsuhide) is the chief of the Metropolitan Police's First Investigation Division, working directly under Soichi Makage. Despite knowing Makage's true identity as the Freeze Roidmude, Nira aids him in controlling the police force while giving the Special Investigations Division grief. The reason behind this is that Nira has an inferiority complex towards Shinnosuke's father Eisuke Tomari, and is actually Eisuke's murderer, having shot him dead when working with him on a bank siege. After Freeze abandons him, Nira aids the Special Investigations Division in reviving Shinnosuke before his role in Eisuke's death is revealed. From there, Nira uses a Neo Viral Core to form a symbiosis with Roidmude 106 to become the Thief Roidmude (シーフロイミュード Shīfu Roimyūdo). After Roidmude 106 is destroyed, Nira forms a new symbiosis with Brain to help the Roidmude achieve his Over-Evolved Form. From there, Nira turns the police and the public against the Special Investigations Division, leading to their arrest, but his underhanded dealings are revealed to the public and after being abandoned by Brain, Nira is arrested by Shinnosuke, finally avenging his father's death.
The Thief Roidmude is one of the three Roidmudes that are brought back from the dead and faces off against Shinnosuke until being destroyed by Kamen Rider Ghost.