Planet Earth continues as usual. Technologies advanced (flying cars, instant meals etc), and power sources depleted. Consumable power sources were estimated to be fully depleted the year 3000, and so research began for new sources of power.

The Energy age gets it's name because this was when it was first discovered that talented warriors could channel their 'ki' or fighting aura into beams and use this skill to travel at immense speeds without the need for a vehicle. The first combat androids were created in Russia to fight the wars of man. Most androids were female because Russia knew that american men would hesitate in shooting a beautiful young woman. Only the units with the suffix 100 to 199 of any given series were male. No other country ever made an effective combat android.

From here commenced the shortest age in all human history. It was meant to be a normally sized age but things eventuated after just 100 years of this age which changed the world drastically. Many now refer to this as the "Short Age", and because of this there were some lived to see three different ages of men.

The reason for the name of this age is that humanity in its infinite wisdom found a new fuel source that was finite but capable of creating immense amounts of power. This energy source was named "Mana" and was literally the planet's lifeforce.

Automotive companies successfully managed to team up and convince the general public that ki manipulation was something that only combat androids could acheive, and ironically the belief of the masses led to this becoming a fact.

The Russian government realised that without humans able to utilise ki attacks, its L337 series of ki-androids could defect and destroy mankind without much effort. They then created the L473 series of marksmen androids with the firepower to destroy ki-bots and a special compound skin that almost completely negated energy attacks. The ki-bots were hunted down and de-activated by their later models. Soon the Russian government had confirmation on the de-activation of all but 2 of the L337 series andriods. L337-192 was AWOL and L337-035 was MIA assumed dead.

Nothing brings about the end of an age faster than the imminent destruction of mankind. More specifically, the planet gave it's answer to the drain on it's lifeforce by creating a demon with the power of the entire planet, and direct orders to eliminate all human life on earth. This struggle between man and earth was quickly realised as a new age, and probably the last age in the story of man.

This demon was named 'Ragnarok' was born out of the amazon jungle, and after two years had eliminated all traces of man in South America and was moving through Mexico into North America. There were very few capable of even slowing its progress, and as the US was almost utterly destroyed, a group of heroes emerged from across the world to attempt to destroy the Ragnarok demon. The initial attack was in vain and most of the group were slain. Ragnarok moved across the Atlantic into Europe and continued the world's cleansing. It was documented by scientists that Ragnarok was destroying the countries that used the most Mana energy in order. This 'Ragnarok Theory' hypothesised that after the US and Europe, Russia would be the next target.

The heroes re-gathered and for the second time were unsuccessful in destroying the menace to mankind. A warrior named Forseti after the Norse God of Justice was the only warrior to survive both the first and second assaults on Ragnarok.

Russian scientists found a single weakness in the demon. By utilising the Ragnarok theory, if they created the largest Mana Generator in history, Ragnarok would be drawn towards it. Also the 'Ragnarok Theory' stated that if you drain the planet's lifesource, then Ragnarok's power would also decrease. The Russian government was happy to build such a generator, as it may be their only chance at survival. They called it the Ragnarok Crisis Mana Generator. Construction of the RCMG was started with great haste, and all Russia needed now was warriors capable of destroying this menace.

The Russian government sent units L473-003 and L473-004 were sent to find the warrior named Forseti so that he could lead the final assault. They found him surprisingly easily as he was staying at an inn in Moscow. However, Forseti and Ayumi (remaining heroes of the second battle) were demoralised and unwilling to fight, believing there was no way to destroy this demon. L473-003 disclosed some of the information about Russia's resistance plan, and this sparked a glimmer of hope in Forseti. He agreed to fight this last time till either he or Ragnarok had perished.

As Forseti and Ayumi waited for the day where they would decide the fate of the world they happened upon a familiar face. It was Miss Leet who had taught Forseti at All Midgard Primary Boarding School. She re-identified herself as Unit L337-035, and said that she would join the pair in the final fight. Over the next year they lived on the outskirts of Moscow and Forseti slowly grew very fond of 035. Ayumi, in turn, was madly in love with Forseti, but at this stage oblivious to his feelings towards 035.

As 2008 dawned, RCMG was started up and the earth seemed to moan with pain. Ragnarok swept across Russia in a torrent of anger and the final resistance was mounted.

The scientists figured out the exact damage they needed to do so that Ragnarok would be damageable without threatening the life of the planet. By delaying Ragnarok with their strongest attacks, they slowed it down enough that the generator drained almost a third of the world's lifeforce. At this stage Ragnarok started to take damage from the attacks. By continuing this strategy and stopping the generator before the world died, Ragnarok was finally destroyed.

Ayumi discovered that Forseti had fallen for L337-035, and so out of spite she stole each of their most prized possessions. From Forseti she stole the Legendary Masamune blade, and from L337-035 she stole the upgrade chip that allowed her to control ki blasts.

Mankind starts to rebuild from where it left off, but for one major difference, and that was not the lack of population. All of mankind heard of what destruction was wrought and why the earth found it needed to summon a demon against them. All countries that managed to escape impending doom joined together on a worldwide pact to never use Mana for energy again.

However not all were convinced. Although Russia closed down the Ragnarok Crisis Mana Generator, they soon found that the other countries of the alliance were so focused on rebuilding their cities and setting new borders across the world that they could use Mana energy in small doses without anyone knowing.

Most countries closed their borders, but again Russia took the initiative and claimed the most of Europe as its land. They created a new city, the largest in the world, and powered it entirely with Mana. As the city was officially made the capital of the world in 3500, this was stated as the beginning of the Rebirth Age. As all the workers at the new Mana generator NRCMG (New Russian City Mana Generator) were androids without emotion chips, only the Russian Government knew this was what created the power for their immense city.

Japan (being the primary setting of Mirai Mugen) had been happily sitting in a second feudal age with Emperors in power as apposed to a central government. With the news of Russia's new capital, the current Emporer instructed scientists to travel to this city and re-discover the arts of modern buildings and technology.

By the start of Mirai Mugen in 3960, most of Japan was re-built to its former technilogical glory, and for the second time man started researching the logistics of intergalactic travel.