Tetsuko "Teco" Hayasaka hails from a medieval Japanese village, sharing a close bond with Goro, a swordsman-in-training dedicated to defending their home from bandits. Their peaceful existence shatters when the enigmatic Owl arrives, pursuing a potent crystal. Amidst the chaos unleashed by Owl's followers, Tetsuko is flung backward through time to an unfamiliar era.

Thrust into this disorienting displacement, Tetsuko reveals bravery and intellect. She quickly adapts to strange environments, encountering diverse cultures and individuals during her temporal odyssey. Her analytical mind and independent spirit guide her through complex challenges. Tetsuko tends towards reserve and introspection, often appearing emotionally detached or aloof, especially under pressure—a demeanor aligning with observations noting her curiosity and analytical nature alongside perceptions of coldness.

Alongside Goro, Tetsuko journeys across various historical periods. Their quest focuses on unraveling Owl's true motives and goals, evolving into a struggle to safeguard their village and prevent a larger, world-threatening catastrophe orchestrated by Owl. Throughout these trials, Tetsuko's loyalty and steadfast commitment shine, particularly within her trusted partnership with Goro.

Her narrative connects thematically to enduring bonds across time and space, reflected in her character theme, the song "Time Stranger ~ Teco no Tehma".