| Ok, we're going out to battle, so let's go with high spirits!!!
I might be McDohl, you don't know me.
Koyu is one of the Lampdragon Bandits, along with his oath siblings, Gijimu and Lo Wen. He lost his parents at a young age, but Gijimu adopted him as a sworn brother and he became a bandit with him since then.
Under their influence, he grew to be a dedicated and obliging youth, able to compensate for his lack of strength with quick thinking in battle. He was also good friends with Marlowe as each has what the other wants, personality wise.
During the Dunan Unification War, Neclord's zombies attacked the Lampdragon Bandits' stronghold and Koyu ran to the New State Army in order to ask its leader for help. After having his request granted, Koyu led a party of New State soldiers to the Lampdragon Bandits' stronghold and to Tinto City. After Neclord's defeat, like Lo Wen and Gijimu, Koyu joined the New State Army.
After the war, Koyu occasionally visited Marlowe in order to marvel at Marlowe's scholarship, while continuing to work under Gijimu.
As such, he accompanied Gijimu to Milit Village on Gustav Pendragon's command when the village was besieged by bandits calling themselves the Fire Bringer and helped to defeat them.