Natsume is Aya's best friend who supports her in everything that she does.
Natsume is actually one of the heads of the Platonic Heart along with her brother Haruki and Miko, who is actually her cousin. Natsume hates Aya because Aya's father caused her mother to be mute. The cause for this was because her mother lost the Platonic Heart competition several years ago, which was established by Aya's father. The whole reason why it was established was because Aya's father's parents were murdered by Natsume, Haruki, and Miko's mothers' father, and Aya's father wanted to get their mothers to compete in order to get revenge on them for what their father did.