Takanashi Rikka - At the beginning of the anime series, Yuuta tries to avoid Rikka due to the fact that she has 8th grade syndrome (something he is trying to forget and leave behind). However on the first day of High School she approaches Yuuta and reveals to him that she knows about him being the Dark Flame Master. On that same day Rikka loses her wallet, and Yuuta is forced to take her home due to the fact that Rikka lives a floor above Yuuta's apartment. From this point on Yuuta seemingly takes on the role of a caretaker. When Rikka runs away from her grandparent's home, Yuuta chases after her. Rikka forgets her key and they stay in Yuuta's apartment alone for the night. At this point, Yuuta begins to wonder about his feelings for Rikka. During the preparation for the school festival, Rikka slips off the roof of the school building but is saved by Yuuta. After being rescued by Yuuta, Rikka refuses to let go of Yuuta and the two embrace. After some initial awkwardness Rikka is able to confess to Yuuta first and the two form a "lover's contract." When Tooka reveals that she will be leaving for Italy, and that her mother will be taking care of Rikka, Yuuta tells Rikka to take off her eyepatch. This prompts Rikka to leave behind her chuunibyou. When Rikka decides to move back in with her grandparents, Yuuta is confused but soon realizes he was the cause of Rikka's departure. After reading a letter he sent to himself from his days as the Dark Flame Master as well as later learning (from Kumin) about how Rikka began with her chuunibyou, Yuuta races off on a bike borrowed from Isshiki to Rikka. Yuuta (who now accepts his and Rikka's chuunibyou) asks Rikka to form a contract with him. Rikka realizing that Yuuta is accepting her for who she is, leaps into his arms and the two are reunited. Yuuta takes her to the "etheral horizon," so that Rikka can say her goodbyes to her "papa" and move on. At the end of the series it is revealed that the chuunibyou Rikka has returned to living in the apartment above Yuuta's. Yuuta fully accepts chuunibyou, but still finds it embarrassing.
Shinka Nibutani - Yuuta met Nibutani by accident whilst coincidentally arranging their looks at the train station. After realizing that she was the class representative and his classmate, Yuuta developed feelings for Nibutani, prior to establishing a close relationship with Rikka. He had imaginations of Nibutani harboring feelings for him. The two got along well with each other especially when Yuuta becomes unintentionally a class representative. At some point, Nibutani asks Yuuta out on a date, but it turns out to be only a feat for her to find her book and destroy it, thus revealing her chuunibyou side. Like him Nibutani wishes to get away from her eighth-grade syndrome. This made him empathetic to Shinka and no longer has feelings for Shinka, though he understands her and continues to assist her in her life problems.