Sword and Shield

Hirate said all of this passionately. 

Many people in the room nodded but they all have a hard time accepting that.

If not for the fact of all the factors mentioned by Hirate, there is a huge chance that Earth would be ravaged by that Demon king and no one could stop it

This is also the time when they found how dangerous it is to keep travelling through the Multiverse. 

It now makes sense why even those advanced civilization and advanced world would not easily mess with the Multiverse.

And there are also the guardians of the Multiverse that one simply does not provoke. 

Travelling through the Multiverse, treating it like some kind of door you could simply opens and close without circumstances is a wrong way of thinking

Each time, they open a door to another world, it weakens the barrier between realities and one day, maybe some powerful being from some other powerful universe would come.