Ajin

If you are chosen by the bizarre black sphere known as the Gantz, you are already dead—yet you might be able to reclaim your mortality. First, the Gantz demands that you undertake brutal missions of madness, killing aliens hidden among the population. It is your only chance and you have no choice. You must play this disturbing game. And if you die again—and you likely will—it’s permanent.

Mireille Bouquet is a professional assassin, and a very good one at that. But when she follows up an e-mail from a young Japanese girl named Kirika Yumura, inviting her to take "a pilgrimage to the past," her life becomes even more dangerous than it already is. Now, with a haunting melody invoking the memory of an event long past, Mireille and Kirika decide to work together to find the truth about a thousand-year-old organization that has controlled both of their lives since before they were born. And the only clue in their search, the only thing Kirika remembers about herself, becomes their working codename: a name designating an ancient fate, of two maidens who reign over death—Noir.

An immortal being takes on the form of a human boy, wandering the earth and experiencing the pains and joys of life throughout his story without end.

In response to the worsening crime rate, Japan creates Tokyo Butei High, an elite academy where "Butei" or armed detectives hone their deadly skills in hopes of becoming mercenary-like agents of justice. One particular Butei is Kinji Tooyama, an anti-social and curt sophomore dropout who was once a student of the combat-centric Assault Division. Kinji now lives a life of leisure studying logistics in order to cover up his powerful but embarrassing special ability. However, his peaceful days soon come to an end when he becomes the target of the infamous "Butei Killer," and runs into an emotional hurricane and outspoken prodigy of the highest rank, Aria Holmes Kanzaki, who saves Kinji's life and demands that he become her partner after seeing what he is truly capable of.