Kasumi grew up learning the Todoh school of Aikido and Kobujutsu, taught to her by her father. As her family's sole heir, she does all she can to stand up for the Todoh way. When Ryuhaku stayed at Southtown to settle an old score with a man named Takuma Sakazaki, Kasumi remained in her house, waiting for her father's return. A couple of months later, she got some bad news: Ryuhaku had been defeated by Ryo Sakazaki, Takuma's son and hasn't been seen since. She decided to fight Ryo and anybody else in order to avenge her father. Unfortunately enough, her mother, Shizuka, did not like that idea. But she eventually makes peace with him and returns to Japan with her mother.
In 1999, she not only reunited with King, but also teamed with Blue Mary and Li Xiangfei to try to stop NESTS. Later in 2000, Kasumi rejoined Mai, and the two teamed up with Yuri and Hinako Shijou. While Kasumi had some reservations about teaming up with Yuri (mainly because Yuri is a Kyokugenryu Karate practitioner), Kasumi knows that she has to live under a family code of ethics and accepted Yuri as her teammate. This was a sign that Kasumi matured a little bit as time passed by.
In the newest KOF game, The King of Fighters XI, she teams up with Malin (who had teamed with Athena Asamiya and Hinako Shijou in KOF 2003) and the bitter rival of the Sakazaki family, Eiji Kisaragi to form the Anti-Kyokugenryu Team. She, Malin, and Eiji were beaten up by mistake by an angered King, who was more angry at Robert, Yuri, and Takuma, and thus, were victims of circumstance.