Get ready for tinfoil. "O world, in our final moments, why did it have to be him?" (Sana's brother to die)
Seriously though, the o world thing made me ponder something, what happens to the world itself when a TERMINAL dies? does it die along with it? Does it get left behind as the entities flee to a new one? Is the world itself the TERMINAL itself? And tinfoil comes again, is the T for TERMINAL? ok, enough kidding around:
I agree with the Chinami thing, but as a counterpoint, if Chinami is going to die, then it would make sense that it happens right before a reset, as she can come back right after. People don't die in kumon-mi after all, and if Chinami's a character she too is meant to achieve completion, thus she can't not be there (for long).