seems like itsuki hasn't received a definite name yet? i can see these these proposals: itsuko, itsukihime, itsuki (with different kanji), taken from http://wiki.sos-dan.com/wiki/Itsuki_Koizumi_(female) is itsuki the version accepted on danbooru?
I could be wrong on that, but I think Koizumi Itsuki 古泉一姫 (with different kanji) is the popular version. Other variations don't turn up anywhere near as much if searching with the Japanese characters on Google.
