Nisfa is a beautiful girl with long, straight black hair that cascades gracefully down her back and a flawless, fair complexion. She hails from the wealthy, renowned Kim family—millionaires who own numerous companies. Hers is a harmonious family; her parents adore and constantly support her, accepting her completely, including the fact that she is bisexual and attracted to women. Nisfa is a motorcycle enthusiast who rides a black ZX25R and frequently wears black outfits and jackets.

Haeun is a beautiful girl with soft, lovely blonde hair falling straight down her back and a flawless, fair complexion. She, too, is a rider—owning a black CBR150R—though she doesn't belong to any specific gang; she simply loves exploring and visiting great places.

Nisfa leads a motorcycle gang—a large group of fellow enthusiasts—but it is unlike most others; they are neither malicious nor criminal. Known as "Black Angel," the gang often helps people on the streets—assisting pedestrians crossing the road, escorting people home, or sharing food with those in need. They do not engage in foul play, illegal street racing, or dishonest schemes. One night, while Nisfa was on her way to the café where her gang usually hangs out, she spotted Haeun on the roadside with a flat tire. Nisfa rode over, killed the engine, lifted her helmet visor, and said "Hey there, pretty girl—what's wrong with your bike?"