In 5556 AD, the Olympus Mothership T-001 arrived in the orbit of Titania, a planet in the [redacted] system of the [redacted] Galaxy. The mothership was a floating castle with 100 floors and a diameter of approximately ten kilometers. It carried 5,000 colonists and 258 crew members in hibernation pods, who had made a 140-year journey from Earth. The mothership was also equipped with hundreds of small spaceships, powered by a new form of nuclear energy called the "Machine Heart."

Before the colonists could be sent to the surface, the MECHA units, which were controlled by the mothership captain, Kagiyama Shimpei, were sent to explore the planet and prepare a safe landing spot for the transport ship. The MECHA pilots were shocked to find that the plants and animals on Titania were massive, and the atmosphere had double the oxygen levels as Earth. The landing was delayed until the MECHA could build a suitable settlement for the colonists.

The MECHA pilots became the only humans allowed to live on Titania and were divided into three teams: builders, miners, and gatherers. The builders were responsible for terraforming a plain and building the foundation for the first settlement. The settlers consisted of 20 people who were sent to experiment with life on the planet. With the help of the gatherers and miners, the colonists were able to build new MECHAs and equipment to survive on Titania.

One year after the arrival, in 5557 AD, the colonists had built additional MECHA units to speed up their work on the planet. Lieutenant Barrett Stone was appointed as second in command on the ground while the mothership captain remained on the mothership to take care of the remaining colonists. Lieutenant Stone led the first exploration mission based on reports from the miners and gatherers who had witnessed strange creatures lurking around them. The lieutenant divided the MECHA pilots into three teams to explore the surrounding areas. The West team explored the forests, the North team explored the mountains, the East team explored a nearby desert, and the South team explored the ocean.

The Western territories exploration team reported finding a dense, far-reaching forest with large trees and various creatures. They also discovered a dark cave that led to a massive room covered in moss, remains, and puddles of water. The team encountered what seemed a sentient golem who was able to communicate in English. The golem introduced them to the Primordial, one of the inhabitants of the planet, but later on, they revealed themselves as druid-made Mecha piloted by Besten. The Besten were peaceful and curious, and they shared some of their territories with the colonists.

While the colonists were establishing contact with the residents of Titania, an asteroid collided with the mothership, causing a malfunction that made it lose altitude. The mothership started falling towards the planet and was visible from the planet's atmosphere. The colonists on the planet and on the mothership panicked, but the Primordials quickly landed to help the mothership land safely on a rocky platform made of five Primordials. This event disrupted communication with Earth.