Doh-Hyun is one of the Four Guardians of Heaven and perhaps the strongest of them all, the "Black Turtle." He is the second of the two Guardians ordered to capture the Angel Princess. Despite his observative nature, Doh-hyun finds out that Dong-young is a girl but still does not make the connection that she is, in fact, the angel princess that he was ordered to capture. He has a crush on the Princess(Chun-yoo/Dong-young).In later volumes of the manga, it was found out that since they were still little kids, Doh-hyun has liked the Princess and wanted to protect her until the end. He has great feelings for Dong-young and even thought that marrying her in the end will be a good idea. After Doh-Hyun found out Dong-Young was the Princess, Doh-Hyun became more protective of her and he threatens that if he finds her in a bad situation once he will be taking her back to Heaven. Later he begins to develop feelings for MI-Hyang So-Wal and they become a couple.
Growing up in a family of seven (Father, mother, himself, younger brother, twin younger sisters, youngest brother), Doh-hyun was often left to take care of his younger siblings as his mother and father did not like the respinsibility. However, Woohyun (and some 'kidnappers') help him to realize that he actually cares for them a lot. He is shown to have been around Woohyun from a young age.