is demon slayer: kimetsu no yaiba episode 3 filler?

The Demon Slayer Corps…an organization that's been hunting down demons since ancient times. Sakonji Urokodaki begins Tanjiro's training for the Final Selection, the test for those wishing to join the corps.

His training begins with navigation of a mountain riddled with booby-traps, dry sword swings, waterfall immersion, and breathing techniques. A year later, Sakonji informs Tanjiro that he has nothing more to teach him, and gives him one last hurdle to overcome in front of a giant boulder...