Gumi has short, light-green hair and large green eyes. She's somewhat short and dresses in frilly and bright clothing. She is also usually seen wearing her goggles on her head.
Gumi can be very childish and insensitive at times. She's a bit clueless and tends to say whatever pops into her head. Sometimes she ends up hurting others,but she apologizes afterwards. She's also very playful and loves to prank others. But occasionally, Gumi will show her serious side. Overall she's a bit of a wild card.
Gumi is human and doesn't have any special powers. She can sing very well though, but she isn't a siren.
Gumi is something called a Vocaloid, which pretty much means she's supposed to be a computer-created pop idle. In Reality she and the other Vocaloids are Youtube sensations and sing many different kinds of songs. In DD, though, Gumi and the others are fully human and aren't in any way synthetic.