Saya is a new heroine who only appears in Little Busters! Ecstasy. In the daytime, she is a popular girl in her class at Riki’s school due to her attractive face and figure, though is known to be a natural airhead. However, at night, she can be found at the school wandering around in order to obtain a “treasure” from those she calls the “darkness executives,” and even has to fight them for it.
Saya’s true identity is Aya, a normal girl with a father as a doctor, who volunteered in various countries that are not well-off. Since they had to move frequently, she did not have enough time for any deep relationships with others or school. During her childhood, she briefly befriended Riki during her short stay in Japan, when they played soccer with each other. Despite that, she still had to leave Japan with her father due to his work. Aya continued traveling during several years until she and her father finally decided come back to Japan and have a normal life. After a short time since she return to Japan, Aya became involved in an accident due to a flood. Is clearly hinted that she died in that accident, since at that time, the artificial world still hasn’t been created, and it’s even confirmed by herself later on her route.
When the artificial world was created, her wandering soul which still having a lot of regrets and unfulfilled wishes enter to the artificial world. Inside, she materialized as Saya Tokido, a character from Kyousuke’s favorite manga, which incidentally happened to be her favorite as well. Due to this, Kyousuke originally thought she was created due to his hidden desire, and intended to leave her alone. After seeing her interacting with Riki, he realized that she was actually an “interloper” to his world and he tried to tolerate it until some point, however, Riki got involved with Saya so much that her existence caused him to stray away from the others LB members, due to various reasons: He did not want to involve the other Little Busters members with the “darkness executives,” and fell in love with her so much that his feelings for Saya remained, even after the “resets”, at the point that he prefered to spend his time with Saya, rather than with the others, which contradicts the main reason for the creation of the artificial world: let Rin and Riki end up together and become stronger in order to overcome the tragedy and support to each other, since they’re the only two potentially survivors. At some point, Kyousuke realized that he has to make Saya leave the soonest as possible in order to come back to the original purpose for the creation of the world. This is implied during the “replay” portion of her route where all the traps that used to be just merely a prank become lethal, and everything turns into a replay game.
The head of the “darkness executives,” Tokikaze Shun (who is actually Kyousuke role-playing the main antagonist from Saya Tokido’s manga) tells Saya at the beginning (and each subsequent replay) that if she want to leave the dream world, she just has to pull the trigger on herself, since ‘this world’ could be hard for her to handle.
In one of the last loops, Kyousuke says to Saya that he can’t allow her to repeat the loop anymore and ask her to leave, since they can’t continued doing that forever. During that scene is revealed that Saya always knew about the secret of the world and the youth she always wanted was inside of the artificial world. She also says that everybody inside the world is kind and gentle, including Kyousuke, since as she stated, he could get rid her anytime if he really wanted to but he didn’t do it.
Finally, Saya acceded to leave the dream world and Kyousuke promised to grant her final request. Saya ask for a last time loop in order to have another chance to meet with Riki, defeat the final boss and obtain the treasure. Kyousuke agreed with it but since the identity of the treasure is unknown, Saya ask him to turn the treasure into a biological weapon. In the very end of her route, after her final request was fulfilled (and all her other wishes too), Saya shot herself in the head to leave and disappear from the dream world. In the final scene of Saya’s route in the VN, she woke up in someplace, apparently being a kid again.
The ending of Saya’s route is a interpretive ending which allows the viewer give their own interpretation and meaning about it.