Sequel to Gunstar Heroes. Gameplay is similar to that of the original title, but with a fixed set of weapons and the addition of close combat techniques.
Taking place after the destruction of the "God of Ruin" (also known as Golden Silver, the final boss) at the end of Gunstar Heroes, the explosion created four moons orbiting the Earth. However, many years later, the creation of a fifth moon reveals a plan to resurrect the malevolent Empire and Golden Silver once again.
Most of the new characters bear both the names and likenesses of their equivalents in the original game (such as Blue, Yellow, Green, Pink, Kain, Kotaro, Orange, Black, Gray, and Smash Daisaku). The main characters combat the Empire under the organization called The Third Eye, (abbreviated "3YE") under the names Red (female in the North American version, ambiguous in the Japanese) and Blue in recognition and tribute to the characters from the original game, and along with Yellow on the team, they are known as Gunstar Super Heroes. The Gunstars must travel to the moons, stop the resurrected Empire, and recapture the Treasure Gems, four mystical stones with an unknown power that had driven the story in the last game. The game has different storylines based on what difficulty is chosen and which character the player is playing as.
The gameplay makes a number of changes from the original Gunstar Heroes. The controls for Red and Blue no longer distinguish by the Free and Fixed Shot and both have more advanced, equal and versatile controls. The Throw from the original is taken out, and various melee attacks are now performed by using the A and B buttons in combination with the D-pad. The ability to combine different weapons is absent - instead, the player has the option to select from three weapon types at any time in the game. The game also uses a supercharge meter that fills as the player defeats enemies; using this energy allows the player to fire a powerful attack.
Source: Wikipedia, "Gunstar Super Heroes", available under the CC-BY-SA License.