|First Appearance||Alliance of the Golden Witch|
Kasumi Sumadera is Kyrie Ushiromiya's younger sister.
Kasumi's older sister, Kyrie, was originally going to be subjected to an arranged marriage. However, Kyrie preemptively married Rudolf Ushiromiya and left the Sumadera family. As a result, Kasumi was torn away from her existing lover and was made to marry Kyrie's original fiancé.
Kasumi appears as vindictive and easily angered. She typically disguises her threats as "serving matcha" to others, a metaphor for a form of torture.
Alliance of the Golden Witch
In 1998, Kasumi pursues Ange Ushiromiya during Ange's journey to Rokkenjima. She confronts Ange while she is looking for the Kuwadorian and reveals the torment she endured as a result of Kyrie Ushiromiya leaving the Sumadera family.
- Kasumi's typical threat of "serving matcha" is echoed by ANGE-Beatrice during Twilight of the Golden Witch.