Korea's Supreme Court on Thursday confirmed a 20-year sentence for a private cram school director for sexually assaulting two sisters from the age of nine over a span of 11 years.

The court upheld the original ruling and rejected the appeal of the 60-year-old man, who was charged with violating the Act on the Protection of Children and Youth against Sex Offenses.

Between April 2010 and April 2021, the man sexually assaulted two sisters at different times who attended his after-school private institution in Cheonan, South Chungcheong Province.

In 2010, he sexually molested a 9-year-old girl and in April 2014, he offered her free private classes on weekends, during which he sexually assaulted her. The abuse continued until May of the following year.

After the girl quit the cram school, the man shifted his attention to her younger sister, who was aged 10 at the time, and sexually molested and assaulted her on multiple occasions from 2015 to 2021.

During the police investigation, it was determined that the hagwon director had taken advantage of the victims' worries about hagwon fees, due to their family's financial difficulties. The sisters, now in their 20s, explained that they were too concerned about their mother, who was in poor health at the time, to report the crimes until they became adults.

In the first trial, the court justified the duration of the sentence, highlighting that the defendant had exploited vulnerable minors who had no means of defending themselves, leaving lasting psychological trauma on the victims and their family.

Both the prosecution and the man appealed the decision, but the court in the second trial dismissed the appeal, citing the principal's failure to fulfill his duty of protecting minor students, his absence of prior criminal records, and the level of physical coercion involved.