Shima operates as a soldier within the Magical Girl Special Operations Development Unit (M-Squad), a specialized Japanese Self-Defense Forces unit commanded by Colonel Yoshiaki Iizuka dedicated to anti-magical terrorism and combat operations. M-Squad integrates both human soldiers and magical girls. She maintains close bonds with her fellow members, especially Kaede, and among the unit's four core personnel, Shima possesses the most cheerful and upbeat personality, providing a distinct contrast to M-Squad's often grim duties in magical warfare.

She shows deep concern for the well-being of the magical girls under the unit's purview, particularly her combat trainer, Kurumi Mugen. This protective nature aligns with her role providing direct operational support to magical girl personnel during missions. Her responsibilities include managing tactical communication relays, such as patching Asuka's speech through to all allied units during the battle against the Babel Brigade. Shima's documented role focuses solely on her duties within M-Squad operations and her interpersonal dynamics with its members.