She is a member of ITEM, led by Mugino Shizuri.

Despite being a powerful Psychic, Saiai is one of the most mellowed-out characters in the group; she isn't a screw-up like Frenda, nor is she as frightful as her leader, Mugino. She enjoys bad movies and likes to tease others, Shiage in particular because of his reaction to anything sexually suggestive.

She also likes to add "super" (超, chou) to her remarks.

Her ability is the Level 4 Offense Armor (窒素装甲, Chisso Soukō?, lit. "Nitrogen Armor"), which she uses to control the nitrogen in the atmosphere to create a few centimeters of solidified nitrogen to act as a barrier. She can use this to attack and defend. Like Accelerator's AIM vector shield, the primary function of her ability is to create an armor of super-compressed nitrogen around her, she fights a sniper in volume 15 and Academy city's special sniper rifle is shown to have no effect on her other than to knock her backwards a little. Because of her ability, she carries around a small amount of nitrogen for use at all times.