Multiverse

The Multiverse (多元宇宙) is a collective group of multiple universes, parallel dimensions and alternate timelines. The amount of entities in a multiverse may vary from a few universes making up a lesser multiverse that is part of a much larger composition, to an infinite number stretching across all of existence, time and space.

Background
Countless eons ago, the amount of dimensions in the Multiverse was very numerous until the threat of the Final Gods significantly decreased that number by consuming and destroying trillions and even quintillions of universes for the purpose of reducing all of reality into an infinite husk of absolute nothingness where only they alone can inhabit. This started a great multidimensional war between the Final Gods and the Ancient Gods, extremely powerful entities who guard and protect the balance of the cosmos in all dimensions. After billions of years of fighting, the Ancient Gods were losing and the Final Gods were continue to devour more and more dimensions. As a last resort, the Ancient Gods, led by Bandaios, sacrificed all of their remaining power to not only drive away the attacking Final Gods led by Ygso'Gurath into the farthest depths of time-space possible, but also send the remaining universes that they could find into an isolated pocket dimension and merge them to form a new universe.

The resulting universe that formed from the merger was created over 16 billion years ago, and in the following eons, elements and aspects from the previously existed universes that were merged lingered.

The Mahou Kaiju Series "Multiverse"
For 16 billion years, the single universe that came from the merging of multiple universes remained a singular universe within a pocket dimension, but was very unstable to the point where even a slight disturbance or interference with the flow of space-time and the state of its continuum (i.e. time travel) could cause everything to spiral down in chaos.

When Tatsurou Akiyama and Yukimura Katsuki traveled back in time to correct prior events and save Yukikaze Mizuki and Rinko Akiyama, this was the catalyst to break down the stability of space-time in the universe, as the resulting time travel split the universe into two dimensions based on two different timelines: one where the Tatsuro successfully saved Yukikaze, and the other where he never did. The universal split also caused a spillover in the space-time, which in turn created a third universe, that is identical to the other two but is time-displaced.

As a result, there are three universes sharing identical quantum wavelengths and the same spatial-temporal vicinity in the pocket dimension:
 * 1) Main Universe – The main setting where the majority of the events of the Mahou Kaiju Series take place.
 * 2) Evil Universe – The alternate universe that was created as a result of Tatsurou's time travel, it is the location of the original unaltered timeline where Yukikaze and Rinko were never saved and things went downhill for the Taimanin and the Justice Alliance. The Earth of this universe is ruled by the Vampire King and Queen Edwin Black and Asagi Igawa.
 * 3) Another Universe – A byproduct of the original universe's split into two, it is nearly identical to the other two universes, expect its temporal placement in the same quantum vicinity that all three universes share is displaced and therefore not the same as the other two. The events of the first season of The Taimanin Force take place in this universe.

Black, Asagi and Blackout attempted to forcefully merge the three universes, using Quasarmageddon Chaos as their vessel and means to do so, but were ultimately foiled. After the Universal Alliance defeated Azathoth-Omega, order and stability in the space-time continuum was restored once more when the three universes become one again.

Trivia

 * The Mahou Kaiju Series’ multiverse concept is inspired by cross-dimensional stories from various superhero comic books in addition to cross-dimensional stories in other genres (namely Science Fiction and Science Fantasy), such as those made by Marvel Comics and DC Comics.