Naoki Ishida, a 39-year-old former junior high school teacher, left his position amid unresolved personal struggles, transitioning to part-time work as a cram school instructor. His relentless perfectionism fuels an aversion to missteps and lingering regrets, shaping his wry self-assessment as a "troublesome old man." Now performing in a middle-aged idol group, he navigates the friction between aging physicality and societal perceptions of maturity, channeling a disciplined mindset honed through years of education to pursue both individual and collaborative ambitions.

The kanji in his given name—"straight, direct" (直) paired with "tree" (樹)—mirror his dual nature of unyielding resolve and adaptive growth, while his surname, blending "stone" (石) and "field" (田), reinforces an identity rooted in resilience and pragmatic endurance.