It's the worst adaptation to date of this famous manga. Hiroaki Samura's original is a 30-volume samurai revenge epic with famously realistic art and some questionable content. It's spawned a Takashi Miike live-action movie and two anime series, of which this is the first and worst. It looks pretty, but...
(a) it's incomplete. I'm not blaming it for this, since the manga ran from 1993 to 2012, but it's still a significant strike against it today. The 2019 anime covers it all, while the Takashi Miike film skips lots of it but at least does a proper ending. This, on the other hand, just stops. It doesn't even bother taking on an anime-original ending. It's almost funny in how blatantly it doesn't give a damn about it.
(b) it's boring. It's doing that slow, pretty samurai drama thing, with wood instruments on the soundtrack and a paucity of interesting characters. It lacks immediacy. It's assuming that samurai are inherently interesting. Men with no sense of humour kill each other with swords. Well, yes, good, but what next? Admittedly, some characters escape this trap and become watchable, but not all.
(c) As for the female characters, almost all of them except Rin are currently or have worked as prostitutes. (The title sequence is boobs and killing.) The show deserves praise for not being stomach-turning (unlike the 2019 anime), but that's still hardly inspiring.
MANJI = one-eyed, scarred ex-thug who's killed a hundred innocents but is better behaved these days. He's immortal. He can be freed of this "curse" if he kills a thousand evil men.
ASANO RIN = teenage girl who saw "Ittou-ryuu" samurai kill her father and rape her mother. She wants revenge, but she can't do it alone. Hello, Manji.
The show's at its best when focused on either the women or on that smug artist in ep.4. (Rin goes looking for a second bodyguard, but her candidate only cares about oil painting.) Manji's entertaining too. The relationship between him and Rin is one of the show's strengths and and helps keep it going. I also quite liked the show's themes, with episodes that address the wisdom (or otherwise) of revenge, pride, selling yourself and the shame of being saved by a woman. ("Even a monkey can become a samurai.") Mortal enemies can have calm conversations, visiting each other's houses for tea.
The art's impressive, but its brand of realism can make it hard to tell apart the different samurai and prostitutes. Personally, though, I don't even like it as much as the 2019 anime's art, which looks punchier.
Don't watch this show. I wouldn't have recommended it even if there weren't other, better adaptations. Those ones are more gripping and visceral. That said, though, the 2019 show is deeply unsuitable, so that's the one thing its 2008 predecessor has over it. This isn't bad as such and it has some good episodes, but it's got the worst versions of Manji and Rin... and, yeah, it's boring.