A group of siblings were separated from their parents while fleeing from an imperial alien army that has a goal to destroy 1000 planets to make their deity ruler immortal. The siblings were taken to earth with the family robot who ends up taking care of them. Over the course of at least a decade, the siblings became teachers for an elementary school as a way to go through civilian life. While in reality they were secretly trained by their guardian robot to become Earth's defense against the same imperial army that forced them to separate from their own parents. In order for them to be reunited with their parents, they must defeat the alien army before it succeeds in making Earth the 1000th destroyed planet.
For being the first Super Sentai series of the 90s, it has a good story. Not masterful, but fairly watchable. What separates this from the other super Sentai shows is that it's the first series were all of the rangers are related to one another. So the bound between them is different from the other Sentai Ranger bounds.
For those who like watching the other Super Sentai shows, will likely to enjoy this series as the story is good, and the female characters are wonderful to know. Especially Five Yellow who is my favorite ranger of this series.