Title basically says all. I've seen the anime and want to start the manga (but skip over the common part). From where should I start?
The first thirteen volumes of the manga are covered, including the first arc (Black Swordsman). Though the manga storyline remains largely intact, many changes were made with the modification or elimination of characters, some of the series' most violent and brutal scenes, and material that would have extended the storyline beyond the planned run of the anime series. Themes of friendship and ambition are more developed and emphasized than those of causality and the supernatural, all of which were made with the approval of series creator Kentarō Miura.
That being said you might still want to read said first 13 volumes, there are many scenes skipped in the anime.