Tanjiro's Journal, Part 1

Sakonji lays out the basics of the demon-hunting world to Tanjiro. The Corps numbers in the hundreds and has battled demons across generations even though the government refuses to acknowledge it, and the identity of its leader remains hidden. He also describes what demons are: creatures that must devour humans, that heal their own injuries, and that some can shapeshift or wield strange powers. Only sunlight or a beheading with a Nichirin blade can finish one off.

Sakonji explains that he serves as a trainer, one of the so-called cultivators who prepare swordsmen for service, and that any recruit must first endure the trial called Final Selection at Mount Fujikasane. He alone will judge whether Tanjiro is ready to attempt it.

Tanjiro's instruction is relentless. He repeatedly works his way down the mountain while its traps grow deadlier, learns to cut along the path of the blade so it will not snap, drills standing back up after being knocked down, and is corrected with a sharp blow when his breathing technique is wrong. Six months pass and Nezuko stays asleep, with a summoned doctor finding nothing amiss. After a full year Sakonji declares he has nothing left to teach, then hands Tanjiro a final challenge.

Tanjiro begins his training under Sakonji Urokodaki and spends roughly a year and a half learning the fundamentals of the sword, breathing, and physical recovery. Throughout this stretch Nezuko remains in an unbroken slumber.

Sakonji sets the boy a seemingly impossible task: split a massive boulder in two to prove he is worthy of Final Selection. After another half year of fruitless effort, an unfamiliar swordsman wearing a fox mask appears atop the rock. The masked figure has no detectable scent or presence, attacks Tanjiro with a wooden blade, and dismisses him as too weak for the Corps.

This chapter belongs to the Final Selection Arc and corresponds to Episode 3 of the anime. The masked newcomer who confronts Tanjiro is later identified as Sabito.

The installment establishes core worldbuilding that recurs throughout the series, including the rules governing demons, the role of cultivators, and the existence of Final Selection at Mount Fujikasane.