Do-Yun grew up in a crime syndicate known as Wanjiao traveling around Quyan while his mother, Cheon Yeong-Suk, fought monsters and handled assassinations for Grandmother Unknown. Starting around age 8, they began to train him as well. He didn't take to the family combat discipline and ended up later studying a heavier, slower fighting style. The primary family members he's mentioned other than his mother, are Grandmother Kyoko and his older brother, Shota.
Cheon Do-Yun started out as a self-confident 19 year old cleric in heavy armor, with his shield and war hammer. While he still wears the armor and carries his shield, his old war hammer has been replaced with a sword made of dragon horn or fang found in a lake during their adventures. He has also become less self-confident and is more prone to periods of worrying and high anxiety about his own place in the world, his future, and the people he cares about.
He is never seen without the blue and white fox mask tied to his belt.
He has tattoos that spiral down his arms almost like he had ribbons
around him. The left is pale blue and the right is white. He has since learned that the markings were, in fact, there since his birth as he'd always casually assumed but were in fact meant to mark him as the payment for a deal his parents had made with the spirit Malegami.