How old is tanjiro - How old is Tanjiro in Demon Slayer: Kimetsu no Yaiba?

The two servants apologize profusely on the dazed Tanjiro's behalf and as they return to their mad dash with him in tow, Oyakata leaves one last parting word to Tanjiro, asking him to pass his regards on to the demon who was aiding Tanjiro in finding a cure for Nezuko.

Tanjiro trained more after the Mugen Train Arc so that his body could withstand the strain of its skills, and was capable of taking numerous forms in succession in his combat against Daki, albeit the whiplash from doing so was rapidly obvious.