Ireia Kitty emerges in the final story arc centered on the Bantorra Library's founding and the origins of key figures. She engages in events surrounding the world's near destruction, stemming from a conflict between the lovers Ruruta and Nieniu. Her actions and presence unfold amid the return of deceased characters during climactic sequences.

She undergoes a significant developmental phase in adolescence. Within the library's power structure, she serves as an armed librarian guarding stone books that contain human memories after death. These librarians undertake perilous global missions as peacekeepers and protectors of accumulated knowledge.

Her role ascends to prominence during the resolution of the central conflict, where she executes pivotal actions. The narrative underscores her contribution at the culmination of events tied to the library's foundational truth. Her trajectory concludes with participation in reaffirming the core message about protecting worthwhile aspects within an imperfect world.