Yu Yu Hakusho1992

Kiyoshi Mitarai a.k.a. Seaman:
The world didn't come to an end when the tunnel opened up, I don't think.

Koenma:
These things don't just happen in an instant. It's not like dropping an atom bomb at a certain time and place. The battle will be drawn out, and those beasts Hiei deep fried were just the first wave. More of the canon fodder will follow soon, but they aren't the ones we need to worry about. There are demons of far greater strength and intelligence lurking in the depths of Demon World, laying low and waiting until they know it's safe for them to pass through to this world. And then, they'll unleash a terror more destructive than any weapon man has ever forged, and that is how the world will end.

Kiyoshi Mitarai a.k.a. Seaman:
But what about the Kekkai Barrier? Won't that keep the really bad demons from escaping? I thought that's why they wanted Mr. Kuwabara's power, so they could use it to break the net that's in their way, but since that never happened, the barrier must still be intact, right?

Koenma:
Kuwabara will slice through it.

Kiyoshi Mitarai a.k.a. Seaman:
Why would he DO that?

Koenma:
In order to avenge his friend's death.

Kiyoshi Mitarai a.k.a. Seaman:
He wouldn't do anything that rash.

Koenma:
You obviously don't know Kuwabara.