Yun-Seong excelled in his swordsmanship early on from the beginning of his training. He enrolled in the Seung dojo and made it to the top within a short period of time. One person that kept Yun-Seong going was Hwang, whom of which Yun-Seong idolized. He wanted to be like Hwang, until he got older, he wanted to surpass him by challenging and defeating Hwang.
Soul Calibur II - When Hwang returned from dragging Seong Mi-na back home, Yun-Seong jumped at the chance to challenge him, to see just how good he was compared to Hwang. Hwang had to decline the offer, however, due to the fact that Japan was getting too close to Korea, and the country needed more defensive units. Hotheaded Yun-Seong didn't see this, that is until Seong Mi-na handed him a Seung family heirloom, the White Storm. The weapon is said to reflect ones deepest thoughts, and it showed him what was more important: Saving their country. Nonetheless, Yun-Seong wanted Hwang to notice him, so he unofficially took up Hwang's previous mission, which was to find the Sword of Salvation.
Soul Calibur III - Yun-Seong's travel led him to a mountainside village. He met Talim, a girl in tune with the winds, as well as a sick boy, who's father experimented on him. Yun-Seong learned more about the Sword of Salvation there, one key factor being that it's evil. Yun-Seong even got into arguments with Talim about the sword, neither convincing the other about the sword. Before leaving the village, Yun-Seong had made up his mind. He didn't care if the sword was evil. He'll make the sacrifice in order to be recognized and respected by Hwang, as well as to save his country.