Rika Sena (瀬奈 りか Sena Rika) is a gifted seamstress and craftswoman. A self-effacing person, Rika considers her life as average, and the least distinguished among her friends, but she is happy to be behind the scenes. She works on costumes for school plays and events. She was best friends with Aya since childhood, and she and Aya have a strange dynamic where Aya will do something selfish towards Rika, but Rika's sheer goodness will shame Aya ... and the cycle continues. At some point before the cultural festival, Yukino asked Rika if she had a special someone in mind, and Rika responded to with a denial and blush. Yukino eventually realizes that Rika has a crush on Aya's older brother Kyo when she again blushed while talking to him. However, Aya has been aware of her friend's and brother's mutual infatuation for some time, and after the cultural festival was over, she supposedly stayed behind to do some work so that Rika and her brother would have dinner without her. Though Rika sees herself as the most average and unimpressive member of the group, Tsubaki points out that Rika is actually the most popular with the "regular guys," i.e. the kind that would never tell a girl how they feel. The men in the classroom tense up, confirming Tsubaki's theory. As such, the only one who sees Rika as unimpressive is Rika herself. With her sewing skills, Rika eventually becomes the designated seamstress of Tsubasa's father, a famous fashion designer, who she is a big fan of.
In the anime television series, Rika Sena is voiced by Yukari Fukui in Japanese and Debora Rabbai in English.