Encounter in the Forest (Part II) is 73th chapter of manga
Sanosuke, who is lost, accidentally finds Anji - the fallen monk - in the forest. Sanosuke seeking more power wants to learn the technique Anji is using to destroy rocks with the shockwave of his sword. Anji tells Sanosuke that he will kill him if he doesn't master the technique in one week, but with a vision of his leader from the sekihoutai (sp?), he is able to overcome his weakness, and masters the Futae no Kiwami.