Akatsuki no Yona OVA EP2 - The Yellow Dragon Zeno's Past, Part 1: The Starting Dragon

The gang has a drinking competition around the campfire, in which Jae-Ha eventually wins by default. During that night Yona almost tell Hak that she likes him. A flashback reveals when Zeno first became the yellow dragon warrior, but he feels useless on the battlefield with King Hiryuu, who is the crimson king, and the other original dragon warriors. Gu-En is the first white dragon warrior, Abi the first blue dragon warrior and Shu-Ten the first green dragon warrior. Although Zeno possesses no combat skills, he has the power to heal very quickly. When Zeno demonstrates his power, King Hiryuu is shocked by this and gives him the crest bestowed by the dragon gods themselves. King Hiryuu and the dragon warriors are feared and targeted by more humans, who either perished or retreated due to the powers of the dragons. After King Hiryuu rests in peace, Gu-En, Abi and Shu-Ten give a heartfelt farewell to Zeno, who stays to look after the castle. As Gu-En, Abi and Shu-Ten disperse their separate ways for twenty years, Zeno realizes that the other three have died due to aging. Zeno takes out an entire army by himself as he mourns the death of his friends.