This anime show is rather Awkward, confusing, sadden, and disappointed. After seeing all 12 episodes it became painfully clear that they didn't put much of the effort of the plot on this story. Having a main character with the death abilities with little emotion and little regret is really, shall I say, way of the line.
But manly I'm sadden and confuse on how the way he kill his, not only his enemy, but his classmates (,eventhough they did try to kill him,) without so much of the effort. The other sadden part that all the classmates have to kill each other in order to survive is really mess up. Especially the part when they can't help the others but to help them self is really unforgettable.
On Episode 7, near the Ending, was that sion summoned the Scientist to know about the main character death abilities. But instead the Scientist got killed by getting his head blow up by his phone device. I was shocked and confuse about why he died for that.
On (last) Episode 12, after sion gave the intel to the main character and attempt to go back to Youchi, she was captured and died of Suffocated by mana. That part sadden me the most. But don't get wrong though, I know she was a bad woman who started it all by broughting them in her world and kill them just for kicks, but I feel sorry that she died before she help Youchi injuries, because in my heart, I think she love him for being his side as a Guard.
Anyway if they made second season I hope they put more effort but less killing straight forward and maybe a little romantic since as well. Otherwise this show would have not been on the anime from the start.