The Virus teleported Kurai with Hikaru. She didn't care what it does with Kurai? Good, because it wanted to have some fun with Kurai.
"You would want to leave the galaxy," the Virus told Hikaru. "Unstable Saraton Energy is one hell of a weapon." The Virus took over the ship again, charged up all the cannons, and destroyed it. One would expect a massive explosion. Yes, that's true, but there's something else, too. A black blob, blacker than a black hole, blacker than black, expanded, and expanded at an exponential rate. It was already spreading fast to start with, but as each second pasts, it gets a lot faster. Anything and everything in its path gets completely destroyed, breaking the laws of conservation. In fact, it destroyed anything and everything in every single way possible, and even ways that are IMpossible, to BE destroyed completely.
How is it able to do this? USE is not bound to existence. It is destructive energy, so it got as destructive as it could. Not even God Fire is able to stop this. USE would simply destroy it with literally no resistance. There is no way to contain this, magic or otherwise. If one used magic, USE would simply destroy the effects.
USE also sucks things in. It sucks things in stronger than a black hole. It can make an entire galaxy collapse, and cause significant gravitational disturbances to distant objects, objects even on the opposite side of the dimension.
This was a big galaxy, so shouldn't this take days, weeks, months, years, even? Nope. This entire galaxy has been consumed within minutes.
The ASF knew this was happening, so they followed Hikaru, cloaked, before this happened.
USE took several weeks before it had spread out and became too unstable to support itself anymore. By then, it had spread far beyond the limits of the galaxy and the local area it was in.