Shigu embodies the Swiss SG 550 assault rifle. She is an honor student renowned for exceptional academic performance and top grades. Her competitive nature coexists with occasional social unawareness, often leaving her appearing detached or absentminded outside academic contexts. She shares a close friendship with Funco, the Belgian FN FNC rifle, and nurtures romantic feelings toward her. This affection frequently sparks jealousy when others interact closely with Funco, manifesting in protective or possessive behavior.

Her physical traits mirror the SG 550's capabilities, granting her high accuracy at mid-to-long ranges and resilience in freezing temperatures. She intensely dislikes losing and prevails through determination during combat. Tactically pragmatic, she utilizes unconventional methods or allies' abilities to secure advantages.

Her background includes participation in school events like jungle wargames and mock battles. During one wargame, she engaged in a sniper duel with G3 and later intervened to protect teammates from Sako, the Finnish RK 95 TP rifle, retaliating by shooting off Sako's side braid. She played a significant role in the Battle of Atami, wounding AN-94 from Red Steel High.

Moments of vulnerability arise from her attachment to Funco, clinging to their friendship because Funco first showed her kindness upon arriving at the school. This dynamic sometimes places her in conflict with others seeking Funco's attention, such as Aug or Sako. Her combat skills and strategic thinking remain consistent assets, though her social interactions occasionally highlight a disconnect between academic intelligence and real-world awareness.