Gotta hate those 'it's dead but not before making a final fatal wound' kind of attacks.
Weird how Kato begs God for Kei to survive, even though he has a little brother he has to return to. And like you said, he should have been sent back alive after defeating the enemy. Perhaps you only survive if you're alive once the actual sending back sequence commences, which transfers people back one by one. If it starts with Kei, then there's enough time for Kato to die.
Ugh, the title of the next chapter is a bad sign...