kirumi left by lying to maki that she needed to use the bathroom in order to check the secret room in the library. While in the library, kirumi discovered the door into the hidden room behind a bookshelf, which she promptly moved out of the way. This triggered kaede's sensor on top of the shelf, and shuichi's hidden camera, whose flash led her over to it. It was around this time that Shuichi had thrown his shot put ball that he had retrieved from the warehouse earlier into the air duct that led into the library. The ball came out of the vent and rolled along the books on top of the shelf that he had set up. The ball failed to hit kirumi but shocked her greatly.

During this time, kirumi, Shuichi, and Kaede were unaware that someone else was aware of their plans to end the Killing Game thanks to the Nanokumas around the entire campus. That someone was the Mastermind of the Killing School life, korekiyo Shinguji. Witnessing shuichi's plan fail through the hidden room, he immediately left it and made his way into the library. Kirumi was baffled as to why a shot put ball fell from up above and while distracted, was instantly killed by korekiyo with his own shot put ball.

Korekiyo took Shuichi's shot put ball that failed to hit her, replaced it with his own, then stole kirumi's Survivor Perk Monopad and made his way back into the hidden room, covering up her murder and making it look like shuichi's plan had succeeded and that he accidentally killed her in his plan to reveal and kill the mastermind.

when everyone came upon kirumi's body, everyone was mystified as to why and how she was killed. Due to the altered crime scene and nobody other than korekiyo knowing what really had transpired, keebo got nauseous at the sight of kirumi's body and ran away from everyone but then tripped, he tried to crawl away due his leg falling off because he tripped, which made kokichi chase after him in worry. Shuichi was shocked and horrified at the thought that he had killed a dear friend instead of his intended target.