The time in the Ultra Dimension is different compared to the Hyper Dimension; one day in the Hyper Dimension is equal to a year or more in the Ultra Dimension. This time flow disparity is stabilized at the end of Hyperdimension Neptunia Victory.
The main continent consists of three nations: Planeptune in the western region, Lastation in the eastern region, Lowee in the northern region, and Eden in the northwest region. The southern continent consists of a single nation, Leanbox.
In the western region there is a continent known as the Hello Continent and in the eastern region there lies the PC Continent. On the mainland, directly west of Lowee, lies Eden, which is considerably small in comparison to the other nations.
There is an island of land in the south which had a small amount people living on it, but no CPU ruling it. In the Extra chapter of Hyperdimension Neptunia Re;Birth3: V Generation, Bamo and Regu were banished from the 4 nations to rule over the island as Sociomobilindusrti.
In this dimension, CPUs are not born as goddesses. Instead, humans must aquire a CPU Memory to become a CPU. Once they have become a CPU, they are then allowed to form their own nations in Gamindustri.
Ultra Dimension's nations, Planeptune, Lastation, Lowee and Leanbox are ruled by the CPUs: Plutia, Noire, Blanc and Vert. There is one Oracle for Planeptune who is Histoire. Eden is ruled by the Seven Sages, who uses Yellow Heart as a figurehead.
In the past, there were no CPUs and Gamindustri was a chaotic place with constant skirmishes and death. The people wished for a time where a goddess would come and create a nation, bringing peace to Gamindustri. Eventually, the Rei Ryghts of the Ultra Dimension stumbled upon a CPU Memory and ate it because she was starved and believed it to be food.
It was then that she met Croire and learned that she had become a CPU and could create her own nation. This resulted in the birth of the nation known as Tari. At first, the people were pleased to finally have a goddess they could worship and a nation they could live in. However, Rei's tyrannical nature began to become far too much for the people. Many of her followers began to turn on her which caused her power to weaken.
Infuriated at this, Rei decided to take matters into her own hands and destroy everyone which had lead to her nation tumbling down and her losing all the faith that she had obtained from her people. After reverting to her human form, she began to think about her actions and began to believe that the fault lied within all CPUs and not herself. This event leads her to believe that CPUs should not be allowed to exist.
Years after Tari's fall, Lowee was founded by the CPU White Heart. For a long time, White Heart was the only CPU in all of Gamindustri. However, after Plutia accidentally consumed a CPU Memory which leads her into becoming the goddess known as Iris Heart and forming the nation of Planeptune.
While Planeptune did take some shares from Lowee, White Heart was not concerned with the loss of shares as Plutia was lazy and did not bother to try and increase her shares.
Hyperdimension Neptunia Victory
In 1989, the Hyper Dimension's Neptune arrived in the Ultra Dimension after being forcibly transported by that dimension's Rei Ryghts. Because of the rules of becoming a CPU were different in her world as opposed to the Ultra Dimension, Neptune was completely stripped of her goddess powers and was nothing more than a mere human. This realization made her seek out a CPU Memory along with Noire to regain her power and prevent herself from aging.
Once Noire had finally become a goddess with the aid of the CPU Memory, she founded her own Nation known as Lastation under the divine name Black Heart. Over the next 3 years, Noire's hard working personality put a considerable dent into Lowee and Planeptune's shares. This concerned Blanc, while Plutia was not concerned as much due to being friends with Noire.
Not too long after, the nation of Leanbox was formed by Vert who was known by the divine name Green Heart. Despite a forth nation popping up, Vert's console had many complaints, and as a result, her shares did not become great enough to impact the other nations.
While initially rivals, the actions of the Seven Sages, a group of people who are against CPU rule that is lead by Rei, cause the four CPUs to work together to stop the organization. The sages were unable to do anything major to harm the goddesses until they created a CPU for themselves. The Seven Sages attempted to kidnap children to turn them into goddesses but repeatedly failed, turning the children into monsters. Eventually they found out that Peashy had became the CPU Yellow Heart by eating one of the CPU Memories Rei had on her when Peashy was kidnapped, so Anonydeath took her from the Basilicom. Yellow Heart founded the nation of Eden, which had a devastating impact on the other nations' shares.
Across the next 10 years, Eden began to gain a large amount of shares. The CPUs would continuously attempt to fight Eden to regain their shares, but they would always be stopped by Yellow Heart and the monster children, which only persuaded their people to belive in Eden instead. This cycle perpetuated until 2002, when the CPUs find out that the Seven Sages use a device to power up Yellow Heart. Shortly after destroying the device, the CPUs discover that Yellow Heart was actually a brainwashed Peashy. The next day, Neptune and Plutia manage to restore Peashy's memory, causing her to leave Eden and became a CPU of Planeptune.
Shortly after that, the Hyper Dimension Rei begins a rampage of destruction that threatens to destroy bothe the Hyper and Ultra dimensions. In order to stop it, the Histoire of the Hyper Dimension connects the Ultra Dimension with the Hyper Dimension through a large portal powered by shares. Due to the overwhelming amount of shares Neptune was able to amass, the portal was able to become self-sustained, and permanently connected the two dimensions together, stabilizing the time flow in the process.