"The bilateral ties have overcome the COVID-19 ordeals and are showing their strength and ever more vigour", South Korea's Kang Kyung-wha said.
"The accused has widely distributed sexually abusive content that he created by luring and threatening many victims", the court said.
Cho Ju-bin, 24, was found guilty of running an online network that blackmailed at least 74 women, including 16 teenagers, into what authorities called "virtual enslavement" by forcing them to send increasingly degrading and sometimes violent sexual imagery of themselves between May 2019 and February 2020.
At a press conference held after the rulings were made, Cho Eun-ho, a lawyer from Minbyun, a social group of progressive lawyers, said, "Law enforcement and the court should use every possible means to protect the rights of victims, who can be empowered to live their lives again by helping bring the perpetrators to justice".
The court said Cho should be removed from society for a long time, given "the gravity of his crimes, the sheer number of victims and damage done to them, his evil influence on society and his (unrepentant) attitude".
President Moon Jae-in has called for a thorough investigation and stern punishment for abusive chatroom operators
Mr Kim said the court chose to isolate Cho from society for a prolonged time, due to his attitude and the seriousness of his crime.
The discovery of the ring sparked a national outcry, with millions of Koreans signing petitions urging authorities to release Cho's identity and investigate not only the ringleaders but also those who participated in the network, paying as much as 1.5 million won ($1,360) to view the abusive videos and images.
Both Cho and prosecutors, who had requested a life sentence, have one week to appeal.
Cho's case has triggered intense public uproar and soul-searching in South Korea over a culture that some experts say is too lenient about sexual violence and continuously fails the victims.
China and USA ally South Korea have traditionally been suspicious of each other but in recent years they have found common ground in economic cooperation and a shared concern about North Korea's rush to develop nuclear weapons.