Setsuko is the firstborn child of Fumikage Tokoyami and Maiko Sadashi. Standing at about 5'2" (157.5 cm) she has a curvy, yet petite figure. Setsuko's name means "Melody Child" in Japanese and is written like this: 節子. She prefers this name and is usually only called 'Melody' by her mother and close friends.

Inheriting most of her genetics from her father, she shares his more bird-like features. Her feather coverage is akin to that of a harpie leaving only her torso bare with dark caramel-colored skin. Because of the higher amounts of melanin in her skin, from her mother's side, her beak is colored black rather than yellow. Her eyes are rust in color, but can reflect a red glare when hit by bright lights.

Her first 5 primary feathers act as her fingers, so she is inherently more klutzy with her "hands". The feathers continue up her arms and stop just before her shoulders. Her thighs are covered in feathers starting at the base of her pelvis and stopping just above her knees. Scales sprinkle her skin from her knees down with 3 large patches along either of her shins.

Her tail feathers sprout from her backside, just above her tailbone, forming a wedge shape. The longest middle feather being about 24 inches (61 cm) and reaching just above her achilles when laid flat.

Though shaped slightly different in sillhouette, her legs have a plantigrade bend like most other bipedal creatures. Her feet are clawed and vaguely human in shape, but she has the added benefit of flexing her feet like a bird naturally would and can grip tightly onto various types of "perches". That being said, she is highly prone to getting her talons caught or snagged in loose fabrics.

Her quirk allows her to dissipate and hide her body in shadows, almost like an invisibility cloak. Ironically she has an irrational fear of what might lurk in the darkness and that can mess with her mental psyche. Overuse of her quirk causes vivid visual and auditory hallucinations and in her panic her brain may play tricks on her to try and "cope", but more often than not, this causes more disorientation. When she snaps out of a bad hallucination it takes her a while to come back to reality.