Sōma is Princess Tomoyo's bodyguard, and a kunoichi (female ninja) of Nihon Country working alongside Kurogane to protect Tomoyo. She appears to be very loyal and protective to Tomoyo,even yelling at Kurogane for getting mad at her.
When the Tsubasa gang came to Nihon Country, she welcomed them and was present to view the battle of Syaoran and his clone. Recently, Tomoyo revealed that Sōma always worries about Kurogane due to his brash actions.
An alternate version of her was seen in Outo country where she was an Oni Hunter alongside her partner. Her weapons were a pair of boomerang daggers.
Sōma is a crossover character from RG Veda, where she is one of the Six Stars, who appears in Nihon Country as the Empress Amaterasu.