Driven by her parents being conscripted into the Terra Abduction at the hands of a mysterious colony, Itsuki joined the Inter-Colony Police in lieu of the secondary education most teenagers are made to undergo. Itsuki dislikes making mistakes and places a heavy emphasis on her work as an ICP officer which forces her into things such as fighting Bougainvillea and Mintao as per the orders of the ICP administration from within the experimental Arc-II-Jl QT-ARMS along with initially being Akiha and Honoka's adversary as the two are collecting components for Leopard. During her time in Surre Academy as the student Mutsumi Shimoyama, Itsuki demonstrates a lack of proper social skills that causes a few awkward misunderstandings—one of which is a very destructive duel with Honoka that suggests that she may also be an Ex-QT. As she spends time around Akiha over the course of the series, Itsuki experiences an extensive anthology of events such as having the Terra Abduction incident demonstrated for her (the EXISTENCEs hypnotizing people into the Pied Piper orbital elevator for use as Nervalist vassals) along with the aftermath of Nerval's exploitation.