Different IdealsKyouko and Sayaka's relationship, to me, serves a number of functions for Sayaka's character. First, Kyouko is initially in direct opposition to Sayaka, which highlights her absolute sense of justice. Kyouko is a magical girl who is completely opposite from the ideals that Sayaka holds. Where Sayaka believes in justice and fighting for the sake of others, Kyouko is of the mindset that magical girls should fight for their own benefit since they are burdened with the task of fighting witches. To Kyouko, the people of the town, witches and magical girls are all part of the food chain. She would rather let a familiar eat a few people to turn into a full witch before killing it in order to ensure she received a grief seed for her efforts. Kyouko uses her magic for herself and only herself. Not surprisingly, this pisses Sayaka off. Kyouko is the kind of magical girl that Sayaka had concerns about moving into Mitakihara after Mami's death. She even states that part of her motivation in becoming a magical girl was to ensure this didn't happen. Yet, here Kyouko was, picking a fight. In turn, Sayaka's spewing of idealistic justice pisses Kyouko off for her own personal reasons. Needless to say the two do not get along upon their first meeting. Sayaka and Kyouko are a clash of absolute selflessness and absolute selfishness.
Further, Sayaka's relationship with Kyouko initially showcases some of Sayaka's more negative character traits. There is no question that she is stubborn, impulsive and completely driven by emotion, almost to a fault, in her first interaction with Kyouko. Sayaka is clearly no match for Kyouko's skill and power as a magical girl, but she stubbornly refuses to stand down because she can't let herself lose to someone like her. Kyouko probably would have killed Sayaka if Homura hadn't interrupted their fight. Blindly fueled by anger and idealistic justice, though, Sayaka is unable to back down. Clearly this isn't a good thing for her well-being. Later on when Kyouko saves Sayaka and prepares herself to defeat the witch Elsa Maria, Sayaka pushes her aside. She refuses to accept help from Kyouko because they are too different and she is going to do things her own way. Talk about being stubborn! Sayaka ends up pushing her body way past her limits because she is too stubborn to let Kyouko help her. To make things worse, she gives the grief seed to Kyouko instead of purifying her soul gem because she doesn't want to owe Kyouko for saving her. If she had taken the grief seed and/or let Kyouko help so she didn't expend so much magic, perhaps her deterioration could have been prevented.
Being in direct opposition to her, Kyouko's next (and somewhat related) function is to challenge Sayaka'a ideals, resolve and feelings, which ultimately helps her grow as a person. Interacting with Kyouko forces Sayaka to recognize that her sense of justice isn't the only one out there. Kyouko's apparent sense of justice involved getting compensation for her efforts and suffering—something she believed she deserved and was only fair. While Sayaka's initial reaction is to stand her ground, this was the first time she really interacted with anyone who held different values from her in the magical girl world. Clashing with Kyouko forces her to consider other opinions more seriously than a distant, "oh, other magical girls don't think this way." Now it was up close and personal. This is especially true after Kyouko shares her story with Sayaka and she realizes that Kyouko isn't actually a bad person, but rather a product of unfortunate circumstances. Sayaka acknowledges that her initial impressions of Kyouko were wrong. Therefore, I have to believe that hearing a more human side to the girl she demonized for having different ideals must have at least triggered some movement away from absolute justice. Sayaka refuses to be friendly with Kyouko because they are too different. But, her willingness to fight to the death over her ideals of absolute justice has dissipated by this point. This, to me, shows that even though Sayaka still hasn't really backed down from her own way of thinking, she has at least acknowledged that someone who holds different ideals isn't a completely terrible person. While seemingly minute, shifting from hating someone who isn't an ideal magical girl to a sense of indifference is a step toward realizing justice isn't absolute—part of her eventual growth.
Kyouko challenges both Sayaka's resolve to fight and feelings for Kyousuke in the PSP game. Sayaka breaks down and cries to Kyouko that everything is hopeless, everything she's done up to this point is worthless because she's doubting why she healed Kyousuke's hand, and she has nowhere she belongs. She feels weak, totally useless and like no one needs her anymore because she can't be with Kyousuke. Kyouko comforts her some, but challenges her negative cognitions by reminding her that even if no one needs her, she is still a magical girl of justice that fights witches. What about protecting the town from the enemy they can't see? What about saving people? What about her resolve? She also asks Sayaka if her feelings for Kyousuke are so weak that she doesn't like him anymore just because he's dating someone else. She asks if her feelings are really so weak that he is no longer worth protecting just because he's dating someone else. Fortunately for Sayaka, Kyouko is able to break through some of the negative feelings and thoughts that lead to her despair in other timelines by doing this. In this sense, Kyouko's functional role of challenging Sayaka helps her grow by giving her the opportunity to hash out and work through some difficult feelings that she otherwise wouldn't have been able to. She is able form a new resolve around protecting the town even without anyone's gratitude. Part of growing stronger emotionally is working through ugly feelings.
Despite their initial differences, Sayaka and Kyouko seem to have a strange affinity toward each other throughout the different adaptations of the series. Through this bond Kyouko is also able to strengthen Sayaka's resolve and save her on different occasions. For example, Kyouko calls Sayaka out to talk after they find out the truth about soul gems. Sayaka had skipped school and stayed in bed, depressed. Once Kyouko tells her story and explains her thinking about being a magical girl, Sayaka seems to have a little more energy. Although Kyouko's intention wasn't to reinforce the differences between them, their talk reminds Sayaka that she vowed to never regret anything and that magic can still be used for wonderful things. She states that she is going to do things her own way but won't lose to or resent Kyouko for doing things differently. Although her burning passion to be a magical girl of justice is certainly nowhere near the level it was previous to finding out the truth, it is evident that Sayaka has some resolve once more. She is able to bring herself to go to school the next day and feel somewhat okay again. So, Kyouko arguably was able to help Sayaka recover temporarily from the blow of losing her humanity. Kyouko is also the only one who is able to prevent Sayaka from turning into a witch—something that only happens in one timeline out of the many she despairs. Like I previously mentioned, Kyouko is able to reach Sayaka by challenging her negative cognitions and reassuring her she isn't alone. Kyouko reminds her she has a purpose: the town needs her to protect them. Further, Kyouko says that she needs Sayaka and wants to be partners. As someone who really wants to be needed and accepted, Kyouko's words mean the world to Sayaka. She didn't have to be alone. She had a place right by Kyouko's side. Where as Madoka couldn't diminish Sayaka's loneliness as a non-magical girl, Kyouko could. Kyouko was able to give her the support she needed in order to pull through and overcome her emotional turmoil.
And I'm Home - Sayaka's FeelingsSayaka's feelings toward Kyouko evolve the more she changes herself. Therefore, I think her changing feelings represent Sayaka's growth as well. When they first meet, Sayaka cannot stand Kyouko. She is appalled to hear her talk about other people as simply part of a food chain and totally snaps when Kyouko takes a jab at her about being willing to break all of Kyousuke's limbs so he is completely dependent on her. She can't accept a magical girl who isn't willing to put her life on the line for the sake of others. Sayaka likely assumes that Kyouko is a selfish girl with no compassion or feelings for anyone but herself. She feels this so strongly that she is willing to battle to the death twice in order to not back down. Her feelings in this stage line up with her belief that justice is absolute and that people are either good or bad. After hearing Kyouko's story and realizing that she actually made her wish for someone else's sake just like she did, there is a minute shift in her feelings. While she has no intentions of being friendly with Kyouko, she acknowledges that her first impressions of her were wrong. She still doesn't like Kyouko by any means, but she probably has some sympathy for her story. As I mentioned in the section above, Sayaka recognizing that Kyouko wasn't really an evil person shows progression from believing justice is absolute. Sayaka is forced to consider that people aren't so black and white.
After suffering greatly and feeling like she's been backed into a corner, Sayaka comes to realize that some of what Kyouko told her about being a magical girl was right. Magical girls aren't perfect, idealized forms of justice. No matter how much good they do, how much hope they create, they will hurt people and spread despair as well. Whether it's just because Kyouko happened to find her at the right moment or because Sayaka felt that affinity I mentioned previously, she admits to Kyouko that she can't remember what's worth protecting anymore. Sayaka even cries and says she was so stupid (for believing in her ideals she fought so strongly for). She openly admits to her that she was wrong and in a way confides in Kyouko her mistake. Since Sayaka has a tendency to isolate when struggling, I kind of took this scene as an indication that they had an unspoken understanding of despair felt by magical girls. I wonder if Sayaka realized how similar the two of them really were even though she so desperately wanted to be different. Kyouko warned her that making a wish for someone else didn't have a good ending, but she insisted that she was different. I think in that moment, Sayaka probably regretted not listening to her attempts to warn her, and that regret was the icing on the cake that turned her soul gem into a grief seed. Some lessons required for growth are painful, after all.
In Hangyaku no Monogatari, Sayaka and Kyouko are very close friends. Sayaka is the only one who retains memories while in Homura's barrier and therefore I think she made a conscious effort to be friends with Kyouko. She later tells Kyouko that the only reason she took the assignment to help Madoka free Homura in the first place was because she realized she did actually have one regret—that she left her behind. I was actually a little surprised the first time I saw this scene because I didn't really understand why Sayaka would suddenly have such strong feelings about her relationship with Kyouko. I thought maybe they did it because fans seemed to support them together. But, the more I thought about it, perhaps it was done intentionally. Maybe once Sayaka reached a state of peaceful acceptance of everything that happened, she was able to see how much Kyouko did for her. Kyouko reached out a number of times to try to help Sayaka and save her. Because of their differences, though, and Kyouko's difficulty with touchy-feely things, Sayaka didn't interpret it that way in the moment. Now that she isn't blinded by negative emotions such as guilt, envy, anger and isolation, she would be in a better position to stop and consider that. Plus, Sayaka becomes a part of the Law of Cycles with Madoka. Perhaps then, like Madoka, she is able to reach a state of enlightenment where she could see that Kyouko sacrificed herself so that Sayaka wouldn't have to be alone. She was willing to bring Madoka with her and take a beating from Sayaka's witch form in attempt to save her. She died in order to stay with her. If Sayaka realized how much Kyouko really did for her sake, it would make more sense to me that she would regret leaving her behind. Or maybe, the red string of fate tied them together and they were just meant to be close. Even after Homura rewrites the laws of the universe and they all lose their memories, Sayaka is shown being friends with Kyouko once again.