Wikipedia - K4 League

The K4 League (Korean: K4리그) is the fourth-highest division in the South Korean football league system. It is regarded as the successor to the K3 League Basic, the second division of amateur K3 League founded in 2017.

Since 2021, Korea Football Association has allowed reserve teams of the K League to join the K4 League.

The South Korea K4 League is a prominent semi-professional football competition serving as a vital part of the country's football pyramid. Organized by the Korea Football Association (KFA), the K4 League features emerging clubs and reserve teams competing for promotion and recognition within South Korea's competitive football landscape. Known for its passionate fan base and developing talent, the league provides a platform for players to showcase their skills and aspire to higher divisions, including the K League 2 and K League 1. With a focus on fostering local talent and promoting competitive football, the South Korea K4 League continues to grow in popularity and significance within the nation's sporting culture.