You Mizuno

She has a strong crush on Takuto, but later realizes that he doesn't feel the same way as her. In an attempt to leave the island, she finds that she is physically unable to, due to her position as a Maiden, with some force causing her day to literally reset to that morning upon reaching a certain distance from the island.

It's revealed that Mizuno is actually an only child and when her mother left, she used her powers to create a clone named Marino and fabricated both of their memories to make it seem that they had always been sisters. After her seal is broken, she leaves the island with Marino in search for her mother.