The 4th King of the Joseon Dynasty. As the creator of Hunminjeongeum, the predecessor to the modern Korean script Hangul, he is regarded by modern Koreans as the greatest monarch in Korean history. Along with King Gwanggaeto the Great of Goguryeo, he is one of the few figures in Korean history commonly referred to by the title 'the Great.' Leading the golden age of Joseon through achievements in numerous fields, he is revered alongside Admiral Yi Sun-sin as one of the most enduringly respected figures in Korean history.

An engineer of Joseon. He invented the Gani (astronomical observatory), Angbuilgu (sundial), Ongnu (water clock), and Ilseongjeongsiyi (sun and star clock).

A civil official and politician of the late Goryeo and early Joseon periods, and a high minister of Joseon. He served five kings from Taejo to Munjong. He held the position of Chief State Councillor for the longest period in Joseon history, serving as a high minister for a total of 24 years (18 years as Chief State Councillor, 5 years as Left State Councillor, and 1 year as Right State Councillor). This long tenure was not entirely intentional; while the King desired his service, it was also due to his unexpected longevity.

A civil official of the late Goryeo and early Joseon periods.

A civil official and scholar of the early Joseon period. He is a representative figure among the Sayuksin (six martyred ministers) who lost their lives while attempting to restore King Danjong to the throne.

A politician, scholar, and diplomat of the early Joseon period.

A politician, civil official, and military commander of the early Joseon period. During Sejong's reign, he pioneered the Six Garrisons (Yukjin). Despite his background as a civil official, he displayed great bravery and was nicknamed 'The Great Tiger.' Entrusted by Sejong to protect the young King Danjong, he served as Left State Councillor and regent but was assassinated during the Gyeyu Jeongnan (coup by Grand Prince Suyang).

The future 5th King, Munjong. His health deteriorated rapidly while observing the three-year mourning periods for Queen Soheon and King Sejong back-to-back. He passed away at the age of 39, just two years and two months after his accession, leaving behind his young son Danjong. Because of his short reign, he could not even finish the mourning period. However, as King Sejong's health declined, he served as regent for about five years starting from 1445, making his actual period of governance approximately seven years. This regency was conducted under Sejong's full trust; from 1447, Sejong even ordered officials to refer to themselves as 'subjects' when addressing the Crown Prince, just as they would the King. Thus, the late years of Sejong's reign are often viewed as the era of Munjong's rule.