Recently, the Supreme Court of Korea issued a significant ruling concerning the starting point of the five-year statute of limitations to bring a claim for unjust enrichment in a case where a game company unlawfully used a third party's musical work (hereinafter referred to as the "Subject Music") as background music for an online game (hereinafter referred to as the "Subject Game") (Supreme Court Decision 2023Da264462, March 13, 2025).
 
On December 18, 2008, the defendant game company released the Subject Game, which used plaintiff copyright holder's Subject Music as background music in certain scenes, and the infringement continued for approximately nine years. In May 2016, the company removed the Subject Music from the Subject Game due to the copyright holder's complaint. Subsequently, the copyright holder filed a lawsuit seeking recovery for unjust enrichment for the unauthorized use of the Subject Music.
 
During the trial, the defendant primarily argued (i) that the statute of limitations was five years under the Commercial Act, and (ii) that the statute of limitations applicable to the plaintiff's claim for restitution of unjust enrichment commenced on December 18, 2008, when the Subject Game was released, and that the claim was therefore untimely. In the alternative, the defendant argued that even if December 18, 2008 was not the date of commencement of the statute of limitations for the claim in its entirety, any claim for unjust enrichment from use of the Subject Music more than five years prior to the filing of the lawsuit was time-barred.

However, the Seoul Southern District Court (hereinafter referred to as the "lower court") rejected these arguments, and ruled that (i) the applicable statute of limitations was ten years, and (ii) the statute of limitations only began to run in May 2016, when the Subject Music was deleted from the Game, on the grounds that it was difficult to determine the exact date of each individual use and because separate claims for unjust enrichment did not arise on a daily basis. 
 
With respect to the statute of limitations period, the Supreme Court affirmed the lower court's reasoning. Noting that the unjust enrichment claim brought by the copyright holder was not seeking the return of a payment itself, nor was there a demonstrated need to promptly resolve the legal relationship as would be required in a commercial relationship, the Supreme Court upheld that rather than the five-year statute of limitations specified in the Commercial Act, the applicable statute of limitations period was the general ten-year term under the Civil Act.

However, the Supreme Court reversed the lower court's decision as to the start of the statute of limitations period for unjust enrichment claims, ruling that the lower court had erroneously interpreted the legal standards on this point. The Court held that the game company, through its unauthorized usage of the Subject Music, accrued new profits on a daily basis, thereby causing damages to the copyright holder. Thus, the Supreme Court held that a new claim for unjust enrichment was established on a daily basis beginning from the date of the game's release to the removal of the infringing Subject Music, and that the statute of limitations for each instance of infringement ran independently for each day.

In cases involving continuous unlawful acts—such as claims for damages resulting from ongoing torts or breaches of contract, or claims for the return of unjust enrichment due to continuing unauthorized possession—it has been established that, absent special circumstances, claims for damages or unjust enrichment are established on a daily basis during the relevant period, with their respective statutes of limitations running independently for each day. This ruling is significant in that the Supreme Court has clarified that the same legal principle extends to claims for unjust enrichment arising from the continuous unauthorized use of copyright protected works. We believe that the clarification provides guidance for similar cases moving forward.