Tohka Shishigaya operates as a sniper in the elite Class A unit based at Mihama Academy, now a covert facility for the defense organization SORD. She executes long-range precision missions alongside teammates skilled in diverse combat disciplines.

Unresolved trauma concerning her parents lingers, with the specifics of their fate undisclosed. This emotional burden resurfaces during operations, particularly when confronting memories of a broken promise made to a childhood friend. That past failure fuels her fierce determination in critical moments, exemplified by her declaration during a high-stakes manhunt that the team must succeed "even if it means crawling home on our hands and knees."

Her personality blends pride and competitiveness, especially evident in her interactions with teammate Murasaki Ikoma. She openly challenges Murasaki's self-proclaimed ninja abilities, creating recurring friction within the group. Despite this rivalry, she mentors new recruit Megumi Kumashiro in sniping techniques.

An overseas mission to locate a SORD deserter forces Tohka to confront her traumatic memories directly. This operation compels her to reconcile past failures with current responsibilities, marking a pivotal moment in her emotional development. Her commitment reflects a transition from carrying unresolved guilt toward embracing her role within the team.

Her combat effectiveness as a sniper remains consistently demonstrated during SORD's high-risk operations against threats like the extremist group The Fatal Answer, reinforcing her status as a key tactical asset.