Key the Metal Idol is an anime OVA series that was released in Japan in 1994, continuing through 1997. The series consists of fifteen episodes divided into three "programs". First Program consists of episodes 1 through 7. Second Program is 8 through 13. Third Program and Final Program are episodes 14 and 15 respectively. Key is a serious and somewhat dark drama with elements of science fiction, supernatural, and action.

The central character of the story is Mima Tokiko (aka "Key"). Key is a robot, crafted by her scientist "grandfather", Mima Murao. Every year, on her birthday, "grandpa" builds Key a new body--one size larger. Upon his deathbed, Murao reveals that Key no longer has to remain a robot: she can become human with the aid of 30,000 friends. Key must do this quickly before her battery runs down. However, some very powerful men are after Key and the secrets her body contains.

Key the Metal Idol is a unique series in many regards. It was originally produced and sold as an "experimental" title. Therefore, the original release media (VHS Tapes and LDs) were priced very low, at 2,500 yen for a single-episode tape or 5,800 yen for a 3-episode LD. This was less than half the typical price of OVA titles at the time. As the series progressed, the episode lengths and volume costs continued to increase. The final volumes were priced 9,500 yen each, which was in line with other titles at the time.

Key is also unusual in that the episodes are of varying length. The first thirteen episodes are approximately 25 minutes each. The final two episodes are 95 minutes each.

In addition to the OVA series, music CDs and Radio Drama CDs were issued.

Source: Wikipedia