Baekje

Baekje was ancient kingdom on the Korean Peninsula from 18 BCE to 660 CE. Baekje was also called Nam Buyeo. According to the Samguk Sagi, a historical record published in ancient Korea, Baekje was founded by Onjo at Wiryeseong (the present-day Han River area in Seoul). Baekje was one of the Three Kingdoms of Korea together with Goguryeo and Silla. Beakje, Goguryeo and Silla tried to expand each of their lands by allying and making war against one another. 
In the 4th century, Beakje conquered almost every southern part of the Korean Peninsula and flourished by accepting Buddhism and reforming its system. Also, due to its advantageous natural environment, Baekje easily traded with China and Japan. Especially Baekje established goodwill relationships with Japanese rulers of the Kofun period and transmitted its advanced culture such as pottery and Buddhism to Japan.
However, in the 5th century, Baekje was defeated by Goguryeo. It suffered the loss of its capital. Baekje moved its capital to Ungjin. In 6th century, King Seong decided to move capital to Sabi to restore Baekje's glorious past. Baekje was ruined by Silla at 660. Although Baekje was destroyed at that time, many ill-fated attempts were existed to restore Baekje from its descendants.