Woo Hyun is one of the Four Guardians of Heaven, the "Blue Dragon". He is also one of the two Guardians ordered to capture the Angel Princess. When they were all little, Woo-hyun teased Ah-hin while thinking that she was Ee-jung because he had a crush on her. Even after a few years, Woo-hyun still likes Ah-hin and tries to make it up to her even with her bitter rejections and Ee-jung's cold warnings,but in the end, he makes Ah-hin his girlfriend and even gets engaged to her. He is also one of the students at Dong-young's school and hunts down evil spirits with Doh-hyun, his cousin.
Woo Hyun has short red hair and eyes. At the start of the series he keeps his hair back with a hariband but changes this in an attempt to impress Ah hin (which fails). Among the four guardians, Woo Hyun's battle clothes are the most modern looking and the least similar to traditional korean clothing (or traditional 'heaven' style clothing). This does change however (not in the actual plot of the manga) as seen in a picture of the four guardians (perhaps a reference to their future looks) and he also dons traditional clothing when in heaven but not battling. Like all heaveners, he is very good looking (especially as compared with humans), as can be seen when he obtains a girls phone number after she also pays for his burgers when Doh Hyun runs out on him at the restuarant.