- Main article: List of I.O.N characters
- The heroine of the series, named after positive ions. She happens to be a psychic and falls in love with Mikado Hourai.
- A high school student interested in psychic powers. He is the president of the Psychic Power Development Research Club. Mikado also worships a fictional superhero, Psychic Man.
- Main article: List of I.O.N chapters
I.O.N was originally planned to be three chapters long. However, Tanemura's editor gradually increased the length until it reached six. It debuted in the June issue of Shueisha's magazine Ribon in 1997.  The manga was collected into one volume in December 1997. Viz Media licensed I.O.N, Time Stranger Kyoko, and Short-Tempered Melancholic for their "Shojo Beat" label in 2007. I.O.N was published by Viz in April 2008.
Tanemura published a one chapter sequel to I.O.N in the November 2010 issue of Ribon Fantasy Zokan Go, a special edition of Ribon. The chapter was also included in bunkobon edition of I.O.N, which was published into in May 2011. It was also published in volume eight of Sakura Hime: The Legend of Princess Sakura.