Mari is tall, and has brown eyes and short brown hair that is partially bleached. Her hair is always tied back with a purple headband. When working in Yu-topia Katsuki, she wears a red jinbei and dark red apron with her name tag on it. She also has two cartilage rings and three studs in each of her ears. She is the only Katsuki family member that doesn't wear glasses.
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.
She has a caring relationship with her younger brother, as evidenced by her continued support of his figure skating career. She is not against asking him for favors to hook her and Minako up with other famous skaters.
Mari is Hiroko's daughter. She helps Hiroko in running Yu-topia Katsuki.
Mari is Toshiya's daughter. She helps Toshiya in running Yu-topia Katsuki.
Mari is decently close to Minako. She accompanies Minako to the Grand Prix Final in Barcelona to support Yuuri, where she and Minako cheer each skater on in the audience.
- "What? That's too confusing. From now on, we'll call you Yurio." (to Yuri)
- "Yurio looks like he's enjoying having tea with someone!" (to Minako about Yuri)
- Mari gave Yuri the nickname "Yurio", and became Yuri's fan because he resembles one of her favorite band members named Takao.
- Mari has a thing for blond boys. 
- Similar to her brother's name, Mari's name means "true worth" (or "true win").
- The toshi (利) in Toshiya (利也) is also the ri in Yuuri (勇利) and Mari (真利).