Source: Wikipedia, "Raiden IV", available under the CC-BY-SA License.
The Cranassians have returned again after numerous defeats against humanity. The World Alliance Military immediately launches the Raiden mk-II and it's blue counterpart, the "Raiden mk-II Beta" to stop the invasion and save the Earth.
The gameplay of Raiden IV is identical to its prior installments, although its level design is different than Raiden III, but it is exactly the same as Raiden II, as the player starts from in-land, over the farms. In later levels the game progresses through a vast cityscape, into the sky, and finally onward to space. The player faces many enemies, powerful stages, and fearless bosses. The Flash Shot System, first introduced in Raiden III, returns in IV. Multipliers are given for destroying enemies that just appeared on screen; the faster players destroy enemies, the higher the bonuses are.