Tohka Shishigaya, a sniper of German and American heritage, received rigorous training from her ex-soldier father and his comrades since childhood. She became her hometown's youngest shooting competition champion. After her mother's death, she spent two years with a private military contractor alongside her father.

Her personality is classically tsundere—belligerent and quick to dislike strangers, yet privately shy and craving friendship despite struggling with social connections. She compensates for her small stature with a forced mature demeanor. Pragmatic and shrewd, she exhibits fierce curiosity but zero tolerance for nonsense. Childhood experiences, like threatening cold-callers with a shotgun, solidified her guarded nature.

At SORD's Mihama Academy, she operates as close-range support, providing cover during missions. She maintains a rivalry with Murasaki Ikoma and endures frequent teasing from instructor Haruto Aoi, which aggravates her tsundere traits.

Her backstory unfolded during a Russian mission to track a gun runner and defecting student, showcasing her tactical skill and fluency in German, English, and Russian. This operation revealed her strained relationship with her father and circumstances leading to her Mihama enrollment.

During the assault on TFA, her resolve faced critical tests. In one outcome, facing imminent capture during mission failure, she committed suicide, preventing teammate Gumi from aiding her and triggering further losses. An alternate timeline saw her survive but lose a leg to a landmine, ending her active duty.

Rare non-combat moments, like lounging on an air mattress in a swimsuit, expose a vulnerability starkly contrasting her usual stern demeanor.