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I completely forgot the name of manga I read some time ago on /a/. It was about high school on island where all of the retarded teenagers with supernatural skills were gathered, and one "normal" girl was sent here as an agent in order to kill them off while avoiding suspicion. She is kinda fucked on the spot, because one of the brightest students is immortal and suspects her from the very start. But because she is well liked and "leads" survivors she's untouchable without solid proof, so it's Death Note-ish in this regard.
Every target has government bounty measured in human lives (one million, two hundred thousands, etc.), even seemingly good natured people with only skill is healing others.