Mari Katsuki is the daughter of Toshiya Katsuki and Hiroko Katsuki and the older sister of Yuuri Katsuki. Mari works at the family hot springs, Yu-topia Katsuki, in Hasetsu. She is the only character seen to smoke.

She is shown to mostly have a laid-back personality, only entering the vicinity when necessary. However, upon seeing Yuri Plisetsky for the first time, she becomes excited, as he supposedly looks just like her favorite band member. Though she usually seems disinterested in what goes on around her, she is supportive of Yuuri and his skating career.

(Source: Yuri!!! On Ice Wikia)