Ajin Part 1: Shoudou
For high schooler Kei and for at least forty-six others immortality comes as the nastiest surprise ever.
Sadly for Kei, such a feat doesn't make him a superhero. In the eyes of both the general public and governments, he's a rare specimen who needs to be hunted down and handed over to scientists to be experimented on for life a demi-human who must die a thousand deaths for the benefit of humanity.
(Summaries provided by MyAnimeList.net)