She once imposed her opinion on Yui, which strained their relationship. Yui was trying to break free to have her lunch with Yukino, and was unable to tell Yumiko, who was fuming for her negative response. Yui was only left with the response of an apology. Yumiko constantly asked about Yui's absence, and warned Yui that she dislikes Yui's attitude. When Yukino barges in and accuses Yumiko of being self-centered, Hayama tried to calm the situation, but both the girls ignored him. The tense atmosphere then drives the other students out, and Yui uses the opportunity to explain that Hachiman and Yukino helped her realize that she can be her own person, and not force herself to do what others want from her, which Yumiko accepts.
Later one afternoon during lunch,Yumiko and her group demanded to use the tennis court, and ignored the fact that Saika had permission to use it. Considering the situation, Hayama make a wager to the service club to have a doubles tennis match, with the winner being able to use the court and to help Saika practice. As Yumiko and Hayato steadily gained the upper hand, Yukino replaces Yui, as the latter sprained her ankle while playing; thus, the service club gained the upper hand.
Yumiko becomes more competitive after learning that Yukino has lost all her stamina. Yumiko refused to back down, even after Hayama's persuasion to consider it a draw. However, Yukino stated that Hachiman will end the match in their favor.
At Hachiman's final serve, Hayato and Yumiko gained the cheering of the crowds, leaving the service club dumbfounded of their victory, as Hayato protects Yumiko from injuring herself.
Later, her attitude slightly changed towards her friends after her confrontation with the more straightforward Yukino. She begin to consider the opinion of her friends; thus, her relationship deepens with them further, especially with Yui. However, her enmity towards Yukino still exists.
In Chiba summer camp, She felt sorry for Rumi, and considered her method of choosing cute friends as the best option for Rumi Tsurumi, who was turned down in a polite manner by Hayama. There, she tried to stand up for Hayama against Yukino's harsh words and coldness towards him.
She later took part in Hachiman's method of breaking the relationship around Rumi, with the persuasion of Hayama, even though she was initially against it.
When the responsibility of class representation for cultural festival committee was focused on Yui, Yumiko raised her strong tone against the class officer and sardonic laughter of Sagami Minami's clique, explaining the requirement of Yui to attract costumers. Thus, her old habits of jumping the gun and imposing her ideas on to her friends without her intention to do so came back, for which she apologized to Yui but was completely smoothed by Hina in a sarcastic way which Yumiko couldn't comprehend Later, she helped the committee under the personal request of Hayama to stall time in order to find the chairperson of the committee, Sagami Minami.
In the field trip following Tobe's request to the club in assisting him to confess to Hina Ebina, Hachiman and Totsuka were included in their group along with Saki. Where, for the first and only time, she had a private conversation with Hachiman. She told Hachiman not to interfere or meddle with her group, especially with Hina. She explained the consequence that will affect her clique's relationship, thus surprising Hachiman about her considerations. This conversation also made Hachiman realize the meaning of the personal request of Hina. At time of confession, Miura wasn’t present. She was, without a doubt, pretending to act ignorant of the current situation; she wouldn’t ask about it, try to stop it, or pay attention to it. In the anime of Episode 2 of season 2, she was shown to gaze the ceiling of the room in distress unable to do anything while the stage is set for Tobe's confession.
Yumiko went to the Destiny Land with her clique.She was informed of Yukino's presence but was slightly annoyed, when she learnt that Hachiman was taging along.While enjoying the theme park, she competed with Iroha for Hayato.
Yumiko arrived to the shrine with her clique (with exception of Hayato) for new year where she was more or less shocked that Yukino knows of the reason for Hayato's absence but went off.
In Episode 11 of season 2 (adapted from Volume 10 of the Light Novel), the rumor of Hayama and Yukino being couple started spreading in throughout the school, which resulted in big change in the atmosphere of Hayama and Yumiko's clique. This adds up with Hayama's reluctant answer to his decision of next year course (either Liberal Arts or Science). This causes an extra pressure on their clique and the posssibility of its breakdown. Yumiko sent an email to the service club regarding to choose between two choice of career path. With Isshiki's explanation, they were able to understand the motive of the request: Yumiko's romantic interest in Hayama.
As the rumors became more and more bothersome in the class, Yumiko confronted the Service Club herself to confirm it with Yukino. Yumiko questions Yukino, about Yukino's relation with Hayama in the past but Yukino said things in a round about manner leaving it un-answered .In the heat of the argument, Yumiko tried to aggressively grab Yukino's arm, but was blocked by Yukino herself. In course of the conversation, Yumiko stated her desire to have an unchanging environment. After a few failures, Hachiman was able to fulfill the request, and Hayama crushed the rumor by using the cheers of Isshiki and Yumiko at the annual marathon.
Following the result of her request by the service club, she choose liberal arts as her career path for her third year. In Episode 12 of season 2, she tried her hand in making Valentine's chocolate for Hayato, with the help of service club.