"It's not like we did it on purpose. But here's the deal."

Ken stands up, looking at Jin. The expression beneath the wireframe is serious.

"We need your firepower. And I want to make sure you're not going to try anything... stupid. And I don't want you to spend forever in a dead world. So either you come back with us or I'll drag you myself."

Mostly, really, he'll feel better with Jin there. Even if Jin is a pain in the ass, he's still his brother. And he wants to make sure he's safe, even if 'safe' is more mental stability than physical at this point. Staying in a dead world is a good way to lose your mind.