Aoi Aiba is a character from the science fiction anime series Sacred Seven. She is the older twin sister of Ruri Aiba, the main heroine who establishes the Aiba Foundation to combat monsters known as Darkstones. Aoi has orange hair and green eyes, matching the appearance of her younger twin.

Aoi’s background is defined by a family tragedy. When she and Ruri were children, a Darkstone attacked their family’s vacation home, an event orchestrated by the antagonist Kenmi. During this incident, her parents were killed, and Aoi’s own powers as a Lightstone activated instinctively for self-preservation. This power encased her within a protective crystal, and she entered a state of suspended animation. While trapped inside the crystal, she did not age, and her vital functions continued to be sustained.

For the majority of the story, Aoi is a motivating force for other characters rather than an active participant. Her crystallized state and tragic fate are the primary reasons her sister Ruri fights against the Darkstones. The Aiba Foundation, which Ruri leads, was originally created by their family to combat these threats. Although she is absent, Aoi’s influence is significant, and she is shown to have feelings for the protagonist, Alma Tandouji, a sentiment that is displayed throughout the series.

Like her sister, Aoi is a Lightstone, a person who can harness their power for positive purposes rather than destructive ones. Her most notable demonstrated ability is the power to encase herself in a protective crystal, a defensive mechanism that preserved her life for years. It is also indicated that she shares Ruri’s capability to transform a gem into a Lightstone and insert it into Alma to help control his immense power, though this ability is not shown being used by Aoi directly during her period of crystallized sleep. Later in the story, Aoi is shown waking up and alive, ending her long slumber.