Masahiro Saki, nicknamed "Chucky," is a second-year Kuzuryū High student and substitute small forward for the basketball team, occasionally stepping in as point guard. Standing 171 cm with long brown hair and rectangular stainless steel glasses correcting his weak eyesight, he dons jersey number 6 and blue-soled white sneakers during games.

Once carefree and overconfident, his lax approach yielded mediocre academic and extracurricular results. A transformative encounter with a driven teammate shifted his outlook, though clashes erupted as he struggled to define his role, particularly with disciplined teammate Kenji Natsume. Tensions peaked during a training camp argument, prompting his temporary exit from the team. During this hiatus, a humbling loss to middle schoolers in a park match shattered his confidence, only for their opponent’s relentless dedication to reignite his drive. Guided by a teammate, he secured redemption in a rematch, rekindling his commitment to basketball.

Though he reconciled with the team, uncertainty lingered. Hindered by average physical ability (5/10) and technical skill (4/10), he pivoted to defensive plays and precise assists, carving a niche as a support specialist. Yet as teammates evolved, his slower progress sparked another clash over training philosophies, leading to his eventual departure from Kuzuryū High. Post-exit activities remain vague, save for a brief cameo appearance.

Raised in Kawasaki, Kanagawa Prefecture, he joined basketball without prior experience. Off-court, he frequented arcades and convenience stores with teammates Momoharu Hanazono, Chiaki Hanazono, Shinichi Yasuhara, and Ryuhei Nabeshima. A pivotal eavesdropped conversation between middle schoolers about basketball’s raw appeal further steeled his resolve. His journey traces a path from craving popularity to embracing a gritty, selfless role—marked by fluctuating self-doubt, clashes with authority, and hard-won growth.