Zhang Jiahao is a very talented medical student who studies very hard each year of med school. He is not a very talkative person, he prefers quiet watching people live rather than actively doing something fun himself. He has two friends - Anxin and Sangwon - and it's all he need to socialize. He wants to be a doctor - anesthesiologist, to be exact.

At night, though, once sun set and moon is out, he's known among dancers as Arno. At night he dances his soul out in the night clubs, on the dance floor of some ruins, on the rooftops of the most prestigious skyscrapers in the city. No one of his dance colleagues and rivals don't know him in real life but everyone whispers about the Arno, the only one dancer watching whom you will be hypnotized. His nickname among dancers is Grace Master for his graceful movements and sharp body control.