Born into a family of elite volleyball players, Sachirō Hirugami followed his siblings Fukurō and Shōko to Kamomedai High after attending Yurisei Junior High—a premier volleyball middle school. There, he cultivated an intense perfectionism, punishing himself relentlessly for errors and scraping his knuckles raw against stone after losses until Kōrai Hoshiumi intervened. In that raw moment, Hirugami tearfully doubted his love for volleyball; Hoshiumi’s reassurance about quitting sparked his evolution from rigid perfectionist to composed athlete. At Kamomedai High, he anchored the defense as "Hirugami the Immovable," mastering read blocking that processed plays calmly and deflected decoys. His court vision rivaled elite blockers like Aone, adjusting mid-play to track trajectories, while his jump float serve—slow then accelerating abruptly—flustered receivers like Asahi and Daichi. Though outwardly serene during matches, he openly taunted opponents and teammates alike, often reining in Hoshiumi’s impulsiveness with sharp rebukes. Against Karasuno, he strategically targeted Asahi’s nerves and adapted his blocks to counter Hinata’s minus-tempo quicks and broad jumps, later downplaying his "Immovable" title when Karasuno’s sync attacks caught him off-guard. Post-graduation, Hirugami entered veterinary studies, reaching his fifth year by November 2018. His academic commitments kept him from watching the MSBY Black Jackals versus Schweiden Adlers match live, despite his brother Fukurō captaining the Adlers.