Change 123 follows Kosukegawa Teruharu, a justice-loving fan of Kamen Raider (a parody of Kamen Rider) and Gettou Motoko, a teenage girl experiencing multiple personality disorder. Orphaned at an early age after the death of her mother, she was taken in by her three fathers, each of whom is a master of a certain style of martial arts or combat-training. Under the care of each parent, Motoko's childhood was subjected to excessively rigorous training, straining her to the point that she developed three split-personalities, Hibiki, Fujiko, and Mikiri, colloquially known as HiFuMi. Each personality is individually skilled in combat skills learned from each master, thus also shaping their personalities. Kosukegawa happens to witness Hibiki ruthlessly kick a perverted man when a shocked Motoko promises Kosukegawa she will do anything if he doesn't reveal her secret. They quickly become friends and Kosukegawa develops romantic feelings for all of Motoko's personalities, and vice versa. However, Motoko feels that something must be done with the personalities as her seemingly unconscious acts of violence cannot be continued, thus she and Kosukegawa set off to supposedly rid of her dormant anger and fuse her personalities into one being.
- ↑ "ちぇんじ123(ひふみ)第1巻 [Change 123 (Hifumi) Volume 1]" (in Japanese). Akita Shoten. http://www.akitashoten.co.jp/CGI/search/syousai_put.cgi?key=search&isbn=231918. Retrieved September 29, 2009.