Hiroshima ( 広島 ) Is a special independent, sentient Dark Matter that exist for a unknown purpose, it saved Allen Walker and stated that his mission is to protect the 14th Noah and kill his brother Apocryphos.
In human form Hiroshima looks remarkably like Yu Kanda in terms of hair and face structure , he wears a yellow trench coat and carries a Katana underneath the coat.
In his true form, he appears as a armored samurai , that wears all white armor and has teal colored hair. He is also taller than both Apocryphos and Tyki Mikk.
In Human form Hiroshima acts the complete opposite of Kanda which confused the exorcist upon meeting him. He deeply cares for Allen/Nea, and even went as far as knocking his counterpart out when he insulted Allen's height.
In his true form he acts the same expect more brutally and more aligned with Kanda's personality, he doesn't answer his enemies threats, he also stated that he will kill anyone wither it be the Noah, or the Order who touches his master.
Not is known about Hiroshima's past or how his human form looks similar to Yu Kanda, at one point in time he was affiliated with the Heart of Innocence. Hiroshima has been around for 7000 years, and spent the last 35 years along with the four Horsemen waiting on Nea's reincarnation. He also worked as a spy for Nea disguised as a level 5 akuma and infiltrated the Noah Family.
Seed of Destruction arc
Hiroshima, appears as a monk eating lunch in the same cafeteria as Allen's friends. He is being harassed for looking like Yu Kanda. He watches as Apocryphos gets egged and listens in on his conversation. Later the two met in the hall where Hiroshima confronts him by slamming him against the wall and into a unused room that was sealed off. Hiroshima demanded to know why Apocryphos was after the 14th noah, Apocryphos refuse to answer. At that moment Tisha attacked Apocryphos despite Hiroshima warning. Tisha's attack caught Apocyrphos off guard and knocked him out the window with a well place kick.
Hiroshima rebukes Tisha, reminding her that despite her love for the 14th she needs to control herself. Later Hiroshima arrives just as Apocryphos was battling Tyki, he and Tisha double teamed guardian and slammed him into a wall. This shocked Tyki as the main Noah family wasn't aware that all the Four Horsemen of Apocalypse reincarnated.