This topic is where we discuss the lore of the series, and believe you me, Virtual-On has an extensive lore. They pretty much ripped out a majority of it in the overseas version of Cyber Troopers Virtual-On MARZ.
Operation Moongate: The Moongate is discovered and the OverTechnology was used to create a new kind of combat robot for the Limited Wars; Virtuaroids. The Solar Cannon within the Moongate is set to go off and it's up to the player to pilot their machine, fight their way past several other VRs, defeat Z-Gradt and destroy the Solar Cannon before it could fire on the Earth.
Oratorio Tangram: L'ln Plajiner, the creator of the Fei-Yen VR and daughter of the man who created the Fei-Yen prototype, starts a new Limited War where the winner gains control of the Tangram, which has the power to manipulate time and space. However, the Tangram is primed to activate and destroy reality, and you have to use your VR to fight your way past other VRs, the Earth Crystal Restraint System "Bradtos", and the Tangram itself.
Force: V-Crystals (the mineral used in the creation of the V-Discs used by the V-Converters on the back of VRs) were discovered on Mars. However, they were found to have properties that prevent most 2nd generation models from working properly, with the exception of the MBV-707 Temjin 707 series. New 3rd generation VRs were developed to have a quality that counteracts the interference of the Mars Crystals.