Ken Yamamura fulfills the role of secretary at 315 Production, known for his friendly personality coupled with a noticeably clumsy streak. Idols at the agency sometimes witness the sheer volume of tasks he juggles. Despite frequently making mistakes, he diligently supports idols and producers through essential behind-the-scenes work. This earnest dedication has fostered trust with the idols he assists.

His specific duties encompass acting as a tutorial guide and information source for agency operations. He prepared catchphrases for idol election posters during events like 315 Production's first general election. Ken also engaged in seasonal interactions, accepting chocolates in a Valentine's Day mini-event and returning gifts on White Day.

Documented traits include Ken's height of 176.0 cm, making him the tallest secretary in the franchise. His birthday is July 2nd. His hobbies include fishing, and he possesses skills in mental arithmetic alongside being ambidextrous.