Rei Jio is a ghost. She was killed by a radio tower that had collapsed on her because of strong winds. She is 17 years old, and is interested in radios. Jio weighs 51.2559 kilograms and is 1.6764 meters tall. Even though Rei Jio is dead, she still bothers going to school because she feels that she must start and finish college first to get formal education. Jio can go to all of the college classes she wants to without anyone noticing since she's a ghost. 

Jio likes radios, bugs, music, circuitry, nature, electricity, physics, and chemistry. She dislikes unpunctuality, loud noises, and thunderstorms. Jio is an eccentric girl who enjoys playing with her radio when she has free time. She also enjoys talking to others using her radio. Jio’s voice is derived from Harigae Seinu’s voicebank, and is voiced by the same person. This makes Jio a derivative. Jio doesn’t sleep that much, but she doesn’t have to bother with sleep because she’s dead. She didn’t know she was dead at first, and she only found out a few days later. Jio is practical and cunning, but can also be naive at times and unaware of her surroundings. She can also be a people pleaser.