Utaha Shiraishi leads the Engineering Department at Millennium Science School, overseeing technological projects and inventions. During a park experiment, her department tested a modified grenade launcher that fired baseballs, accidentally striking another student. She carries a combat robot named "Ikazuchi-chan" (or "Thundergun"), which outperforms hundreds of PMC automata and serves as her primary weapon instead of her issued submachine gun. Her engineering passion fuels eccentric creations like optical camouflage underwear, drill-equipped coffee grinders, and flamethrower-mounted vacuum cleaners, yet she reliably delivers functional results and takes pride in her work.

Occasionally misunderstanding basic concepts—such as mistaking real animals for advanced robots—her technological focus shapes this trait. She collaborated with Engineering Department peers during the baseball-launcher test, reflecting their shared enthusiasm. In combat, she deploys robotic turrets "Ikazuchi-chan" and "Ikazuchi-chan MK-II," whose damage scales with her attack power, while her passive skills boost allied health and her own offensive capabilities.

Visually distinct with violet hair reaching her legs and a cybernetic-winged hexagonal halo, she wears Millennium's standard uniform paired with a lab coat and black tights. She participated in the "On Your Mark @ Millennium" event wearing a cheerleader outfit designed by clubmate Hibiki Nekozuka, developing genuine enthusiasm for cheerleading alongside engineering and deploying specialized cheerbots to support these efforts.