In the course of the history of the Death Note, there has only been
one known case where a human has entered the Shinnigami world
and obtained their powers. This human is known, to the humans, as
Azrael, The Angel of Death. Several thousand years ago Azrael was
the first human to ever obtain a Death Note from a Shinnigami. After
several years of using the note he decided it was about time to test
something. Taking pen in hand Azrael wrote his own name into the
Death Note but nothing happened, or at least, he didn't think
anything happened. After that he went into a small village near
where he lived and it seemed, whomever he talked to would ignore
him. He'd given up half his remaining lifespan for the Shinnigami eyes
and could already see people's names so he wouldn't know either
way if he'd become a Shinnigami himself. Going to the Shinnigami
who'd given him the Note, which was Ryuk, and asking about it, the
Shinnigami told Azrael that a human had never wrote their own name
in the Note and he himself didn't know what happened, only that he
couldn't see Azrael's lifespan anymore. Azrael tested something else,
giving up ownership of his Death Note. Ryuk had already informed
him that once you relinquish ownership of the Note you'd lose all
memories of having it. But Azrael didn't. However, after giving Ryuk
the notebook back the pages, and the book itself started to change.
Normally having a black binding with white letter's the notebook that
Azrael's had returned changed into a white Note with black lettering.
This stunned both Ryuk and Azrael. Ryuk, giving the Note back to
Azrael was shocked as Azrael suddenly grew wings like that of a
Shinnigami, or rather, an Angel. Rather then possessing fleshy wings
Azrael's were more feathery in nature, and rather then being black,
they were white.
Azrael had become the first human who'd obtained all the powers of
a Shinnigami. As the years past Azrael kept a constant eye on the
human world from his new home in the world of the Shinnigami. Ryuk
had more or less became friends with the human-shinnigami and, like
Ryuk; Azrael didn't find much fun in gambling for years. When Ryuk
left the Shinnigami world after dropping his Death Note into the
human world Azrael watched with interest as Light Yagami, also
dubbed by the humans as "Kira" changed the world using a single
Death Note. Finding it a shame when Light died Azrael waited for
Ryuk to return to the Shinnigami world offering him the white Death
Note and telling Ryuk to give him the one he'd managed to keep. It
