At first, Haruka idolizes him because his song, Nanairo no COMPASS , saved her and motivated her to become a composer. Haruka convinces herself that Tokiya is HAYATO when they first met each other, but her belief is crushed when she heard that Tokiya is not HAYATO, but his younger twin brother. Even though he treats her coldly, Tokiya has paid a lot of attention to Haruka ever since they first met, wondering why Haruka always tried her best. After Haruka knew his true identity, Tokiya distances himself from her, but his heart is softened by Haruka's kindness when she states that she wants to hear his songs. Tokiya, surprised, finally realizes that he can start from the beginning again and that he will try singing. Ever since then, he saw Haruka differently, romatically, causing him to begin to look at her as a love interest.
As the series progresses, he becomes more tender with Haruka, trying to make up for his harsh treatment of her early on, and also becomes more attuned to her feelings. After it was decided that STARISH would face HEAVENS in an all or nothing battle, Haruka becomes extremely worried at the prospect of STARISH disbanding, and succumbs to the pressure, which Tokiya notices. He becomes concerned for her, and takes her to a festival to remind her that it was important to have fun as well. When he finally gets her to realize that she'd forgotten that the most important thing was to make people happy, he comforted her as she broke down in tears at her failure. He then pulls her into a tender embrace, which surprises her, and he tells her never to take so much on by herself again, proceeding to ask her to share her pain with him whenever she needed to, implying that he would always be there for her.
In season 3, after QUARTET NIGHT proclaims that they intend to fight to keep Haruka as their composer, Tokiya becomes shocked along with the rest of STARISH. Later, as they all reminisce about how wonderful and pure she is, he says that "before he knew it, being apart from her became unthinkable."
In Season 4 Episode 1, after STARISH pull her away from QUARTET NIGHT, Tokiya holds her and says that "she knows how he feels...he feels the say way she does."
Tokiya's classmate in the S class and fellow member of ST☆RISH. Their friendship is mutual and they keep a regular conversation every now and then. Although, both of them have been more cautious with another as they both realize their feelings for Haruka. Ren loves teasing Tokiya whenever he gets the chance. Ren is also one of the two people that Tokiya calls by first name (the other being Otoya), while Ren calls him "Icchi."
Tokiya's roommate and fellow member of ST☆RISH. On few occasions in their room, Otoya would always start the conversation, having to deal with Tokiya's cold answers, saying he's not obliged or being left confused by his complicated and long explanations. Over the course of the show their relationship starts to loosen up as they get closer. It's shown that when Tokiya was late for rehearsal he tried to call Otoya, and Otoya showed concern for Tokiya because his part time job would keep him out until night, sometimes until morning. They get paired up for the Debut Concert. He is also one of the people that Tokiya calls by first name (the other being Ren).
Tokiya's fellow member of ST☆RISH. Due to similarities in personality, Tokiya and Masato have a good relationship, and they are often seen together or talking to each other. It is shown that both care for each other a lot, and Tokiya has helped Masato on some occasions, notably in Episode 4 of season 2. Tokiya usually listens to Masato's advice, for example, during Episode 8 of season 2. They get paired up for the UtaPri Award Concert.
Tokiya's classmate in the S class and fellow member of ST☆RISH. Tokiya and Syo are close to each other and talk once in a while, though Tokiya is closer to Ren.
Tokiya's fellow member of ST☆RISH. Tokiya and Natsuki aren't shown to talk to each other much, but it is mentioned in the drama CD that they cook together. Tokiya states that if Natsuki is cooking alone, it will become a huge disaster, so in order to prevent that, he has to carefully watch over Natsuki. Natsuki also idolizes Tokiya because of his talent in singing.
Tokiya and Otoya's senpai in the Master Course. Even though Tokiya doesn't consider Reiji a "decent" senpai because of his attitude, they manage to get along, but Tokiya usually scolds Reiji because of his childish personality. Reiji calls him "Tokki," which Tokiya dislikes.
Tokiya instantly forms a kinship with Eiji from the moment they meet, recognizing the young singer's natural gift for singing and dancing. The two of them form a mutual respect and almost a friendship over the course of composing their duet together, and are able to help inspire strength in one(Tokiya) and passion in the other(Eiji). After their duet performance, they are able to part ways as comrades and rivals for the deciding Triple S battle to come.