Utilize the input text as a context reference, choose the right relationship between 'Nomura Securities' and 'Nomura Holdings' from the options.
Options: headquarters location, owned by, parent organization, platform

He previously held senior roles at Nomura Securities Co, the brokerage unit of Nomura Holdings Inc. After he left Nomura, Saito served as CEO of the Industrial Revitalization Corporation of Japan, a now-defunct state-backed turnaround fund that invested in troubled companies.
parent organization