Yumiko Miura

She is Hikki and Yui's classmate who is very popular in Class 2-F, as well as the main female figure in Hayato Hayama's clique.

Yumiko's personality is pompous. Due to her popularity, she is held in highest hierarchy. Hence, she has no trouble making friends and also has little to no understanding towards people who have social troubles. Yumiko doesn't show interest, or mind anyone other than higher hierarchy of the class, which is noted by Hachiman Hikigaya by her attitude towards him. She holds herself in a very high esteem, and is not afraid to use her authority.

Yumiko has be shown to be very good at tennis as it was stated that she won the Junior High Championship. She also demonstrated her skills in the tennis match showdown and she also participated in the athletic festival sports event of cavalry battle for the white team.

(Source: Oregairu Wiki)