Sailor Moon and the senshi are up against a new set of villains: the Death Busters (Professor Tomoe, Kaorinite, the Witches 5, Mistress 9, Pharaoh 90). The Death Busters plan to rule the world by using the energy from the pure heart crystals of innocent victims, but Sailor Moon and the senshi must stop them. The outer senshi (Neptune, Uranus, Pluto, Saturn), also make an appearance, although Pluto appeared briefly in Sailor Moon R.
Source: ANN

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Side story: Bishoujo Senshi Sailor Moon S: Kaguya-hime no Koibito
Prequel: Bishoujo Senshi Sailor Moon R
Sequel: Bishoujo Senshi Sailor Moon Super S
Alternative version: Bishoujo Senshi Sailor Moon Crystal Season III