Sure, Tanjiro masters Sun Breathing in the manga. It's a turning point that showcases his determination and progress. It also ties into the broader story and his quest for justice.
Tanjiro might use his sense of smell to detect hidden threats. Since his sense of smell is super - enhanced, he could sniff out any demons or traps in the way of saving Rengoku. For example, if there are demons disguised as allies, Tanjiro would be able to tell by their scent.
Well, Tanjiro's fate in the manga is tied to his determination to save others and the ultimate confrontation with powerful foes. His death comes as a poignant end to his heroic journey.