Originally a man named Ida who had a son named Keisuke with idiopathic dilated cardiomyopathy, Ida was transformed into Another Ex-Aid when the Time Jacker Ora appeared before him as his son was being loaded onto an ambulance. Ora offered to make a deal with Ida: if he became Another Ex-Aid she would save his son. Ida accepted and was given an Another Watch which he used to transform into Kaijin Rider Ex-Aid.
Another Ex-Aid was later defeated by the combined efforts of Kamen Riders Zi-O and Geiz. However, the Kaijin Rider was revived soon after by Ora, depriving the real Ex-Aid of his powers.
Emu later attempted to convince Ida to stop being an Another Rider, telling him that Keisuke needs his father at his side. De-transforming, Ida angrily says that Emu is suggesting that he just sit around and wait for Keisuke to die.
Another Ex-Aid was later defeated again by Kamen Rider Zi-O with the Ex-Aid armor, resotring Ida to his normal self. Some time afterward, Keisuke was cured of his illness and was seen healthy with his father afterward.