Кая Сёдзу

Kaya is a young woman whose sister was killed accidentally at only 18 years old, 9 years prior, in the first illegal fighting tournament run by Kiyoko Sunomata. Afterwards, Kaya was looked after by Ryuuji's father, who offered her one of his houses to stay in, but she emotionally shut down; it is only when Ryuuji asks her to take in Tsukasa and her brothers, that Kaya begins smiling again. She loves Tsukasa so much that she gifts her her sister's quipao, which Tsukasa goes on to wear when infiltrating the second illegal tournament. Despite knowing that Tsukasa is Ryuuji's bodyguard, Kaya still doesn't like it when she gets into fights and puts her life in danger. After the Kozuki siblings sort out the situation between Iruma and Tenkou, she moves with them into Iruma's apartment complex, and asks Ryuuji to not spoil her anymore.