Meiko is Jin's mentor. Jin is loyal to her. Instead of "Mutou", Meiko calls Jin by her first name. On the other hand, Jin calls Meiko "Onee-sama", and respects her greatly.
Meiko sees Sumire as her rival. Meiko knows about Sumire's potential and wishes an all-out battle with her. On the other hand, Sumire knows that Meiko is a battle frenzy. They had a race once back then where Sumire could defeat Meiko. After being defeated for the second time in the Kobe Special Port tournament, Meiko is satisfied with their race.
Meiko was responsible for Rio's injuries. Meiko once viewed Rio as a strong, promising player. On the other hand, their race really broke Rio's heart.