Matsumiya Toshiko is a classmate and close friend of Lalabel and Teruko "Teko" Takemura. She possesses a tomboyish personality and appearance, frequently wearing boyish clothes and hats, which leads to her often being mistaken for a boy. This androgynous style contrasts with her friends' more traditionally feminine looks. Highly active and athletic, she is a passionate sports enthusiast.

Within their trio, Toshiko embodies the "Butch" archetype against Teko's "Femme," while Lalabel stands as the brave heroine in the middle. These Town Girls find Toshiko contributing competitiveness and physical strength. She maintains a supportive friendship with Lalabel, offering encouragement despite having no magical powers herself. Her straightforward, candid nature anchors their bond.

During the summer vacation shown in *Magical Girl Lalabel: The Sea Calls for a Summer Vacation*, Toshiko travels with Lalabel and Teko to a coastal hostel run by Teko's relatives. When the adults leave temporarily, she helps run the hostel alongside her friends and Teko's cousin Ryota, showing her practical involvement outside school.

Beyond sports, Toshiko pursues piano playing and music composition, dedicating herself to musical studies as part of her character growth. While Teko's family expresses intellectual skepticism about magic, Toshiko's family stance remains unmentioned. Her personal development centers on artistic aspirations rather than magic.

Outgoing, sociable, and spontaneous, Toshiko focuses on the present. Deeply loyal to friends like Lalabel, she also shows cautiousness and occasional anxiety in decisions, manifesting as protectiveness towards her social circle.