Kousaburou Shirakawa, born Masakazu Shimizu, directs the prestigious Kouka School of Musical and Theatrical Arts with a stern, disciplined demeanor and exceptionally high standards for himself and his students. He acts as both mentor and taskmaster, delivering direct criticism alongside constructive guidance, driven by a deep passion for theater and a genuine commitment to cultivating his students' potential as performers.

His marriage to Atarashi Shiori, eldest daughter of the legendary kabuki actor and Living National Treasure Shirakawa Kaou XV, integrates him into the influential Shirakawa kabuki lineage. This makes him brother-in-law to Sarasa Watanabe – erroneously rumored to be his illegitimate daughter but actually his wife's illegitimate sister – and uncle-in-law to kabuki heir-apparent Akiya Shirakawa.

A significant, troubled event from his youth profoundly carved his perspectives on theater and performance, initially fueling a rigid, disciplinarian outlook. Through interactions with students, he gradually reveals greater emotional depth and begins to share these formative experiences, evolving beyond a strict authority figure into a more nuanced mentor capable of empathy and understanding. This character development portrays him balancing strict professionalism with a growing capacity for supportive relationships.

His name, Kousaburou (combining characters for "glitter/ gleam/ twinkle," "three," and "son") and surname Shirakawa ("white river/ stream"), carries symbolic meaning. His behavioral traits suggest strategic intelligence, a strong need for control and independence, introversion, and fierce loyalty to those under his guidance, particularly his students, highlighting his multifaceted role as director, mentor, and integral member of the Shirakawa artistic dynasty.