Rasetsu (羅刹), Is a true main antagonist of Senran Kagura: Shinovi Master -Tokyo Yōma-hen- a sentient Yōma that served Fubuki's mother and thus by extension, Fubuki. She is extremely loyal to Fubuki and Fubuki deeply cares for her. After Fubuki loses her parents, Rasetsu was the closest to family to her.
Rasetsu is a tall Yōma with a quite standard body for the series. She has a grey skin, covered with black feather-like parts, a lizard-like tail, pointy ears, seemingly orange eyes, white hair, and a horn and a third eye in the forehead.
Loyal, Rasetsu served Fubuki's mother until the latter got sealed away, and is protective towards Fubuki, for which she cares deeply, to the point of using all the strenght she can have when Asuka, Homura and Miyabi try to seal her.
Rasetsu served Fubuki's mother, who was known as the most powerful Yōma shinobies ever seen. When Fubuki's mother was sealed away by her husband, Rasetsu saved Fubuki who got surrounded by shinobies that were theoretically ordered to protect her. Injured, Rasetsu met Kurokage, a renegade shinobi who guaranteed his neutrality, and leaves Fubuki to his cares, telling him that she will come back to get her again after she finished to heal. After some time, Rasetsu see Kurokage again and take him Fubuki back.
During the events of Shinovi Master, she is found in the arena's underground by the Crimson Squad and the Hebijo Academy that attempted to sneakingly free the Hanzo team, captive by Fubuki, at their surprise. She shows herself to Asuka and Yumi when Fubuki declares war to all shinobies. She follows Fubuki until the latter's fight with Kagura, and leads the Yōmas during their second invasion attempt, separated from Fubuki.
The fight is first at her advantage, as her overall power defeat all the shinobies attacking her. When Asuka, Homura and Miyabi attempt to seal her forever, she resists Asuka and Homura' combined arts and was about to break the spells after the three were about to success. As she promised to Fubuki to fight with all her power, she reveals her Yōma wild and big form before being sealed forever.