Io is first seen in the film during the first scene, explaining the equipment in her father's van and the reason why they were there to Yuki Ichinose. She plays a minor role for most of the film, with her most important role being delivering some disks to her father. Io is in charge of the Godzilla Prediction Network's finances.
Io is quite rude to Yuki Ichinose at first, calling her an imbecile on multiple occasions, and essentially forcing her to join the GPN. But by the end of the film, Io treats Yuki with more respect and the two begin to display a small friendship. Io is willing to lie to the military to gain clearance to enter an off-limits building, however she does it in the hopes of saving her father before the building explodes. Io does not seem very close to her father, as the two do not talk much to each other when it is not necessary and act more like coworkers than father and daughter. However, when Io reunites with her father in the ruins of the exploded building, she tearfully embraces him, showing that she really does care about him.