This is the second Super Sentai series to be officially released in North America that does not have a Power Rangers counterpart.

In 1970, Doctor Hoshikawa was researching how to transform the planet Sedon into a green, lush world, testing it by attempting to grow flowers.

On the day the first flower bloomed, the Zone Empire launched an assault on the planet, separating him and his wife from their five children.

Arthur G6 took the five children back to Earth and raised them while after the attack, Doctor Hoshikawa safely went to the Planet P16 Milky Way.

The Hoshikawa siblings have been developing the Fiveman technology and training hard upon the possibility of Zone invading Earth.

The five siblings of the Hoshikawa Family (星川家, Hoshikawa-ke) (three brothers and two sisters) were separated from their parents during a sudden Zone attack, sent to board a ship along with Arthur G6 to be raised and learn of the Fiveman technology.

The Silver Imperial Unit Zone (銀帝軍ゾーン, Ginteigun Zōn) is an alien army plotting to rule the entire Milky Way, it flies across universe attacking worlds with its Galactic Warriors.

[3] The entire Fiveman team appeared later in a comic story Power Rangers Supersonic which is in the Boom!