Unlike the past in the Source World, on the Akasha continent, Reiger only needs to use the [Wish Upon a Star] super-level magic to easily cross dimensions and return to the outside from the Hidden Land.
After all, the Akasha continent is not like the Source World; firstly, it doesn't have the power of the three holy swords sealing it off; secondly, the outside and the Hidden Land are not like the Source and Abyss, which belong to the inside and outside of a world.
The Source and Abyss are truly separated by a dimension, making entry and exit extremely difficult.
Whereas the Hidden Land is merely a different space; although it is an independent space, it ultimately still depends on the Akasha continent.
Thus, for the Source and Abyss to interact, a great cost is often required, especially after the three holy swords sealed the Abyss, a cost so great that even the Abyss dared to launch merely one large-scale invasion to destroy "that empire".
