While the friends were riding on the "Mystery Coaster", Hitomi waited until the ride went through a dark tunnel before slipping out of her guard belt, having placed her bag against the seat so she could slide free. She then took her makeshift weapon, her pearl necklace and a grappling hook, and placed the necklace around Kishida's neck. She then attached the hook to the rail, resulting in Kishida being decapitated. Hitomi additionally planted a bloodied knife in Aiko's handbag to frame her (as by this point, Aiko was now Kishida's girlfriend).
However, ace detective Shinichi Kudo (who was riding the coaster with his friend Ran Mouri, and who would later be known as Conan Edogawa after being slipped a poison causing him to digress back to a child's size) was able to quickly deduce Hitomi as the true murderer. After first pointing out that the knife found in Aiko's bag wasn't sharp enough to cleanly cut through bone, he revealed how Hitomi had committed the murder, having utilized her gymnastic abilities to do so. The last bits of evidence proving Hitomi's guilt were the fact that Hitomi's necklace was now missing (Shinichi having found the true murder weapon) and a teardrop Shinichi had felt on his forehead during the ride from where Hitomi was weeping over what she was preparing to do.
Having initially claimed innocence, Hitomi broke down in tears as she confessed to Kishida's murder, angrily revealing how he had broken her heart and how she had been planning to commit suicide later on, before breaking down in a fit of sobs out of remorse for what she had done. While not shown onscreen, Hitomi was presumably arrested.
- Hitomi has the distinction of being the first villainess in the Detective Conan franchise.
- In the English dub, Hitomi's name is translated to Haley and she is voiced by Gundi Eberhard.