Ken Lendoll served as head coach for the Tennis Association of Germany twelve years before the main storyline. He spotted five-year-old Quark Puppe’s potential early, devising rigorous drills like commanding the prodigy to strike numbered wall targets in precise sequences. To bridge their communication gap, Lendoll engineered an ingenious seesaw system with two birds perched in a tree—tilting left to assign challenges and right to mark their completion. This ritual persisted daily for a month, with Lendoll resetting the seesaw each dusk to outline fresh objectives.

Three years into QP’s training, Lendoll was stripped of his coaching title for insubordination but remained at the academy as a cleaner. Undeterred, he clandestinely sustained their regimen, maintaining the seesaw signals and honing the training wall himself under cover of night. QP eventually uncovered Lendoll’s silent dedication, sparking resolve to surpass his limits.

Years later, Lendoll resurfaced among the Germany U-17 coaching staff during their World Cup semifinal against Japan. Witnessing QP’s first-set triumph over Oni, he offered a nod to their past: “Nice game, blue bird.” His steadfast philosophy championed organic growth, urging young athletes to flourish at their own rhythm over succumbing to external demands. The surname “Lendoll” subtly mirrors tennis legend Ivan Lendl’s legacy, cementing his role as a guiding force behind rising talent.