Korean series traditionally did not produce sequels, primarily due to Korea's production structure.

Unlike other countries, a series' intellectual property rights are distributed among production staff in a complex manner, which makes creating sequels challenging.

However, the landscape is changing.

International streaming platforms, especially Netflix, have begun introducing seasonal formats for Korean series. Following this trend, local cable channels such as tvN have also started adopting seasonal formats for their own series and it is quickly becoming a common practice for successful Korean series to produce a second season.

Yet, among Korea's hit series with sequels, only a few have replicated the success of the first season.

The second and third seasons of Netflix's "Sweet Home" failed to reproduce the success of its acclaimed first season amid streams of negative reviews, while series such as "D.P.," "Love Alarm" and "Casino" also saw their subsequent seasons flop, despite initial global acclaim.

Why then, do these Korean sequels often fall short, despite the global success of their first seasons?

Experts attribute this to Korea's tendency to only begin developing sequels after the first season has proven successful.

"Unlike in other countries where series are designed with a seasonal approach from the start, Korea had no tradition of producing sequels, and they are only considered after the initial installment proves successful," said Kim Il-joong, director of global business division at Korea Creative Content Agency.

"This approach can result in sequels that often lack coherence or stretch the storyline too thin, as the original usually had not been made with a sequel in mind," said Kim.

Other experts add that it is also difficult for the sequels of Korean series to be successful, as their strength often lies in their plots.

"Korean series often become a hit due to their compelling plots. Producing a second season for such content can be challenging because it requires continuously developing inventive plots to sustain viewer interest," said Hwang Young-mee, a film critic and director of the Cinerature Cultural Contents Research Institute.

"In contrast, works that succeed due to their engaging characters or other detailed elements tend to have more successful sequels," said Hwang.

"For example, both 'Joker' and 'The Outlaws' had successful sequels because the characters Joker and Detective Ma Seok-do (played by Don Lee) made people come back to see what they would do next," she added.

"Given that many Korean series are plot-focused hits and not character-focused hits, it is challenging for Korean series' sequels to achieve the same level of success," she said.

Despite a number of flops for Korean series' sequels, going forward, adopting seasonal systems is becoming an inevitable trend for Korean producers. Seasonal approaches are undeniably attractive measures for Korean producers to reap profits, as they reduce the risk of total failure by leveraging the popularity of the first season to ensure a certain level of viewership.

In fact, a slew of sequels are waiting to be released in the latter half of this year, including "Squid Game 2," "Hellbound 2," "Gyeongseong Creature 2" with "All of Us Are Dead 2" and "Bloodhounds 2" also confirmed for production.

For Korean series sequels to succeed, it is most essential to assess whether the content can continue effectively in a seasonal format, rather than producing them in the hopes of replicating the original season's success, pop culture critic Ha Jae-geun told The Korea Herald.

Kim of KOCCA also suggested that seasonal formats may not in fact be the optimal way to popularize Korean series.

"Korean series appear to gain more popularity through transmedia storytelling, such as turning webtoons into series, series into musicals, games, et cetera, rather than following a seasonal format," said Kim.