Senna is a young girl with purple hair and a red ribbon tied to it. She has large, orange eyes and is usually seen in a brown school uniform. When she transforms into a Shinigami, Senna wears the standard unseated shinigami uniform with a large, red ribbon tied around her waist.
Senna likes the color red and high places. She's also very curious, constantly darting from place to place. Although she is haunted by brief, randomly-appearing memories of "her" past, Senna generally exibits a spunky, upbeat, and carefree personality.
As stated by Ichigo, Senna is additionally strong-willed, stubborn, loyal, and somewhat outspoken.
Senna also has Shinigami powers and a Zanpakutō. Rukia reveals her Zanpakutō was lost 100 years ago in the Severed world. However, it wasn't revealed as to how Senna obtained her Shinigami powers or her Zanpakutō.
Besides her Zanpakutō, and ability to control Blanks, Senna has shown to be skilled in swordsmanship, and an agile fighter and gymnast. Even in her gigai, she is very agile, able to perform several backflips at once. It is implied she is adept in Flash Steps when she falls and seemingly disappears, reappearing behind Ichigo during a tight-rope walking performance at the Karakura Mall, fooling even Ichigo, who is an expert in Flash Steps himself.
Zanpakutō
Mirokumaru (弥勒丸, Maitreya circle)