Michiko Yamakawa, nicknamed Micchan, hails from Yoshika Miyafuji's village as her best friend, classmate, and second cousin. Unlike Yoshika, Michiko lacks any witch abilities. Both attended Yokosuka 4th Girls-only Middle School, where Michiko often brought injured animals to the Miyafuji clinic for Yoshika's magical healing—once receiving treatment herself.

Michiko harbors a deep fascination for warships and witches, meticulously studying naval vessel specifications with the Imperial Fusoan Navy's Takao-class heavy cruiser Takao as her favorite. Her witch-related interest amplified after Yoshika joined the Navy, driving Michiko to research renowned witches globally.

Post-junior high, she entered teacher training school aspiring to become an educator, though she secretly dreams of enlisting in the Navy to serve as Yoshika's cadet.

In the spin-off "World Witches Take Off!", Michiko hosts "Yamakawa Michiko's World Witches Classroom!"—an educational segment covering witches, magic power, striker units, the Neuroi threat, unique witch abilities, joint fighter wings, and introductions to the 502nd Joint Fighter Wing "Brave Witches" and other characters.

Shy and reserved by nature, Michiko occasionally assisted her grandfather in agricultural work, operating his tractor alongside him.