Itoko Satō directs the Imaginary Science Research Institute, a facility dedicated to studying parallel worlds and phenomena including Parallel Shift and Imaginality. She wields authority at the institute and spearheads research on Imaginary Elements Print (IP), which quantifies the distance between parallel worlds. Her expertise encompasses the complexities and dangers of technologies designed to traverse these realities.

She is Shiori Satō's mother. After divorcing Shiori's father, Itoko raises Shiori as a single parent while leading the institute. Her protective instincts drive her to intervene and prevent Shiori and Koyomi Hidaka from using an experimental IP capsule. They aimed to travel to a parallel world where her marriage remained intact, but Itoko cited the significant risks of manipulating parallel realities, prioritizing safety and scientific responsibility over personal wishes.

Later, Itoko develops a romantic relationship with Shodai Hidaka, Koyomi Hidaka's father and a fellow researcher. Their decision to marry creates familial complications by making Shiori and Koyomi stepsiblings, directly motivating the pair's attempt to elope to another world.

Following a critical accident during Shiori's Parallel Shift attempt—which leaves her physical body brain-dead in their original world while her consciousness (Imaginality) becomes stranded—Itoko collaborates with Shodai. Together, they explain the scientific principles behind Shiori's condition to Koyomi, clarifying that the timing of the alternate Shiori's death overlapped with the original Shiori's consciousness shift, detaching her Imaginality from her body.

Beyond her role as a scientist and administrator overseeing the institute's work, including studies on Optional Shift (controlled travel to specific parallel worlds), Itoko fulfills her duties.