Kotori Itsuka (五河 琴里 Itsuka Kotori?) is one of the main female characters of the Date A Live series. She is Shido's foster sister and secretly works as the commander of the <Fraxinus> airship.
Kotori Itsuka is Shido's adopted little sister; she is also a middle school student as well as a commander to a secret organization known as <Ratatoskr> that deals with extraordinary beings known as Spirits through peaceful means.
5 years prior to the beginning of "Date a Live,"
the young naive Kotori was tricked by a mysterious being that turned
her into a Spirit. Not long afterwards, she was told about the method of
how to seal her power by the same being that had given her that power;
when all was said and done and her power was sealed, Kotori and Shido,
who seems to have the ability to seal Kotori's power, have their
memories of that event suppressed. It was not until during the present
time, 5 years later, that Kotori personally for the 2nd time in her life
uses her Spirit powers to save Shido; this time from Kurumi when he was battling it out in a sense on his school
rooftop. It was not until Shido resealed Kotori's Spirit powers that
they finally remembered that event, and soon afterward they later dub
the mysterious “being” unofficially with the code name "Phantom."
Kotori, being a commander of <Ratatoskr>, would know
certain information that only selective <Ratatoskr> members would
know, while the rest would not.