This is one of my favorite series currently in publication and I even got Torren Smith to sign my copies of it at Armageddicon last year (he was the translator for early volumes).

The story (up to where I've read) takes place in Edo era Japan, when the samurai were dying out and sword schools were stagnating. At the start of the era, an outlaw swordsman by the name of Manji managed to make a huge name for himself by cutting down 100 other samurai and taking their weapons for himself. After accidentally killing his sister's fiancee, Manji decided to make up for his deeds by killing 1000 evil people using his sword skills and immortality.

The series kicks off with that slight flashback before leading into the first arc where Manji is approached by a young girl named Rin. Rin asks Manji to help her avenge the death of her parents and everyone else who was a student at their family dojo/sword school. The two set off in search of the killer who might not have been completely at fault in the first place.

The story is written and drawn by the incredible Hiroaki Samura, whose writing style in the series is very compelling, giving you depth on MANY of the characters from both sides in a very human way and the art is easily the best of any manga series I've read to date. If you've never heard of this guy, he is largely known for his pencil art that Torren himself described as deeply disturbing yet amazing (Samura draws a lot of guro and bondage), almost disbelieving that they were actually done entirely with pencil thanks to all of the detail in them. (Rough paraphrase, sorry, Torren ^^; )

Sample of art here (WARNING: This image is mostly sfw, but the rest of drtenge.com with Samura's other works, not so much)

Now imagine an entire manga series, book after book, with pages full of art with at least 70% of the detail of that image and full two page spreads at 100% and you can see why I love this manga.

As a closing note, I mentioned before that Samura draws mainly guro and bondage works. This series is NOT centered around these though, but thanks to his skill in that area has some mild dismemberment scenes during fights but it's usually just Manji since he's immortal and doesn't care how badly he gets beat up.