Sae Kunisaki

He is trapped inside Hinaki's ring. He doesn't have any memories from before Hinaki let him out of the ring. Additionally, he can only stay outside of the ring for about a fourth of a day. The reason why he is trapped in the ring: He was friends with Yume in elementary school. However, one day his caught on fire, and his family passed away. Sae disappeared. It is revealed that he wished for help, and the ring heard his wish. However, since it could not be fulfilled at the time, he became trapped inside the ring, and the ring lent him some of its power. The price for the wish comes in form of the curse of the ring: every 10 years, it requires a sacrifice: either the soul of the wearer, or the freedom of the one trapped inside. At the end of the 10 years, Hinaki convinces Sae to use the ring's power to turn back time and prevent Sae from being trapped in the ring. It is shown that Hinaki still remembers Sae, in the form of dreams, and that in the alternate timeline, Sae recognizes her as well.