Tanjiro was fighting Joy, Pleasure, Sorrow and Anger, before he smelt another scent, but it didnt belong to Hantengu, it belonged to you. Tanjiro yelled to Genya

Tanjiro - “Genya! Theres another scent! Try find it! Its hiding low on the ground!”

Genya - “dont tell me what to do, Tanjiro!”

he ran off in search for the scent, whilst Tanjiro and Nezuko were fighting Hantengu