Demon Slayer: Kimetsu no Yaiba, Vol. 1

These chapters focus on Tanjiro’s two-year period of training to enter the final selection for demon slayers. Tanjiro’s training can be broken down into three parts: one year of training with Urokodaki, six months trying to break the boulder, and six months training with Sabito and Makomo. In each of these stages of training, Tanjiro gains new skills, both physical and mental. His mountain training evoked strong emotions from readers of the manga and viewers of the anime. While Mount Sagiri does not correspond to a real mountain, the mountain Tanjiro and Nezuko grew up on is largely accepted to be the real Mount Kumotori, near Okutama in western Tokyo. Fans of Demon Slayer began attempting to scale the 2,017-meter-high mountain in streetwear, perhaps seeking to emulate Tanjiro. This led the Okutama Visitor Center to issue a warning to fans of the series, stressing the mountain’s expert-level difficulty and below freezing temperatures (Harding, Daryl. “Fans of Demon Slayer in Japan Are Warned Not to Climb Tokyo’s Largest Mountain,” Crunchyroll News, 19 November 2020).

Urokodaki’s house is located at the bottom of Mount Sagiri. In his role as a trainer of Demon Slayer Corps hopefuls, he uses the environment of Mount Sagiri to help their training. He trains Tanjiro mercilessly and persistently. Later, Urokodaki reveals he never intended for Tanjiro to make it to the final selection, so the training regime was physically taxing for no reason other than to dissuade him (as he has lost students in the past). Tanjiro also endures mental hardship, since Nezuko fell sleep and has yet to wake.

However, Tanjiro continually demonstrates Perseverance Through Hardship by conquering both physical and mental obstacles. Through journal entries, he writes to Nezuko about the dangerous nature of his training. Fear, while often considered a weakness, serves an important biological purpose, alerting people to dangerous situations. For better or for worse, Tanjiro disregards death, as it scares him less than the fear of Nezuko dying. This fear drives him to surpass extremes. He pushes his body to the limit, facing deadly traps and swinging a practice sword “so much I feel like my arms might fall off” (116). Tanjiro faces these physical obstacles with no ego. Even though Urokodaki faces him unarmed, the elder “easily throws [him] to the ground” (119). Tanjiro is never angry or insulted by his relative weakness—he is simply motivated.

Urokodaki uses high-altitude training atop Mount Sagiri to train Tanjiro and track his progress: Tanjiro writes to Nezuko about how he goes “higher on the mountain for my training, each place more dangerous and with thinner air” (120), which marks how far he’s come since his first test. Physiologically, when someone exerts themselves, their blood delivers oxygen to their muscles. This oxygen allows muscles to perform their function. People grow fatigued because their blood can’t provide their muscles with enough oxygen. Often, extreme athletes will train at high elevations where there is naturally less oxygen. Studies have found that doing high-altitude training raises the level of a hormone called erythropoietin (EPO), which produces more red blood cells to carry oxygen to muscles (Park, Hun-young, et al. “The effects of altitude/hypoxic training on oxygen delivery capacity of the blood and aerobic exercise capacity in elite athletes—a meta-analysis,” Journal of Exercise, Nutrition, and Biochemistry, vol. 20, no. 1, 2016, pp. 15-22). This method of increasing one’s endurance and strength is the biological principle behind Urokodaki’s training.

Furthermore, this principle is related to Makomo’s total concentration breathing training. While Urokodaki uses the environment to passively alter and train Tanjiro’s biology, total concentration breathing actively alters his biology. This special breathing “accelerates your blood flow and heartbeat. And your temperature shoots up” (143). This technique serves the same purpose as high-altitude training, but is more sustainable and useful, as the user can actively employ it. When Sabito first fights Tanjiro, he criticizes his approach to Urokodaki’s breath training. He says Tanjiro “just memorized it as fact,” and so his “body doesn’t understand anything” (135). Sabito and Makomo help Tanjiro understand that he can’t succeed by pushing his body physically. There is a psychological aspect to breathing as well as a physiological one. Controlled breathing helps regulate the nervous system, and it has historically been used by practitioners of martial arts, including samurai sword fighters—the inspiration for the Demon Slayer Corps (Radzikowski, Saneteru. "Martial Arts Breathing" shinkanryu.org, 2018).

Urokodaki, Sabito, and Makomo’s training techniques emphasize the extremes demon slayers face. Demons are imbued with strength, but demon slayers are humans with limitations. Tanjiro is a particularly gifted human, whose intelligence and uncanny sense of smell afford him many advantages. However, these natural proclivities are not enough for him to succeed. This emphasizes the idea that even talented people must work hard and practice to hone their skills. During the final selection, Tanjiro’s training is finally put into practice.