On Monday, Hwang Kyo-ahn - the main opposition Liberty Korea Party leader - said he would shave his head to urge the resignation of "criminal Cho Kuk".
A stern-looking Hwang arrived outside the presidential Blue House and was shorn of his neatly parted black hair as the South Korean anthem blared in the background.
"I'm here to pledge my determination by shaving my head," Hwang told the crowd. "I will not step back."
Hwang served as the justice minister and prime minister under the conservative administration of Park Geun-hye, who was succeeded by Moon after she was impeached over a massive corruption scandal.
South Korean politicians have often resorted to shaving their heads in public to express opposition to government decisions and social issues.
Last week two female lawmakers shaved their heads to protest Cho's appointment.
Prosecutors have carried out multiple raids in recent weeks linked to Cho's scandals, and his wife - also a university professor - was indicted for allegedly forging a college award for their daughter.