Blade of the Immortal (Mugen no Juunin) is a story of revenge.
First off, I discovered this series in 2018 with the live action movie by Takashi Miike, and I swear it wasn't bad since it motivated me to read the manga (funny, grotesque, but oh boy the MC samurai was cool asfk, it was enough to attract me).

It takes place in 1782, during the Tenmei Era, since the Tokugawa shogunate is ruling, samurai have less rights. They are watched by the government in order to prevent any rebellion. We follow two protagonists: Manji, the killer of 100 men, and Rin, a young heir from a dojo that isn't anymore.

The story follows Manji, who is cursed by an old lady with Kessen-chû, worms that repair any damage, which makes him an immortal (if an arm is cut off, the worms will go reattach it to the main body for example). No one knows apart from the old lady how an immortal could die, no one has tried, but she gives him the quest to now kill 1000 criminals in order to be forgotten for his past mistakes, and to retrieve is mortality.

Rin's parents were assassinated because they didn't want to join the 'strongest' group of warriors of Japan, the 'Ittô-ryû' and its chief Kagehisa Anotsu. And the old lady suggests Rin to find Manji, because this man may be strong enough to solve all her worries.

The relashionship of the two protagonists grows more and more as the story progresses, Manji will become wiser as Guts from Berserk once he found is crewmates, and Rin isn't a stereotypical distressed lady who needs to be saved, no... He will protect her as if she was his own sister who looked a lot like Rin (killed by the 100 mercenaries who wanted Manji's death because he killed their chief's brother, that was he's biggest mistake) I mean she's weaker than an immortal warrior who doesn't fear death like Manji, but she's a tough one too! He's her bodyguard but she doesn't rest for all that. She risks her life many times. Anotsu Kagehisa, the main antagonist on the other hand hates the bushido (code of honor of the samurai), and thinks that it's outdated. What makes him want to put the Ittô-ryû above the other dojos. A dojo where you can fight how you like, with foreign/trafficked weapons if you want, the only rule being: Fight one on one. As they grow bigger by defeating other dojos (following the traditional bushido), they seek to be recognized by the government. But they are considered as outlaws and to be a threat. The official in charge is Kagimura Habaki and he isn't the tender guy out there. With the Mugai-ryu elite warriors wich lives depend of Habaki (they were sentenced to death for their crimes but to recover there freedom they have to fight for this man), they will track down every member of the Ittô-ryû. (you guessed it, it's not that big of a spoil man)

Of course Manji and Rin will cross their path and as the danger he is, Manji will be targeted even if he isn't the main target.
So those 3 factions will collide many times for honor and justice.

Now concerning the historical context of Blade of the Immortal, even if it's fantastical because of some crazy characters, the setting and the background characters and cities are what is expected from a good historical manga.
I take courses of Japanese language and culture at college, and I personaly love to see accurate elements from this period that I've learned about. Like the system of frontier and free passes, Dejima's island with Chinese merchants and the Dutch, the hidden christians, foreigners who can't put foot on Japan's territory, there is an ainu character too, the pleasure districts, sepukku if you commit a disgrace, the cost of money, calligraphy and ukiyo-e, tekiya who are merchant travelling all over the country to sell their merch from a festival to another... I find all of these things really interesting (like in Samurai Champloo, pros to that).

Now for the technical good points of this manga... The art style, and the panelling is amazing! (why do you think Masashi Kishimoto was fascinated and took inspiration from Hiroaki Samura's technique? Like the 'fish-eye lens' for example)

Samura's art is full of detail, there is movement everywhere, he uses different types of ink to make the battle scenes a lot more intense. Many pages don't have dialogues, they just fight but the angles and the body languages is enough to make those some of the best fights I've ever seen, there is emotion in every stroke they give, you see them shouting their anger. And those fights are for the most uncut, you're let to enjoy every bit of it, and you see all kind of imaginary katana/tonfa/nunchaku/spears and how they're used stratigecally, where you are geniunely curious about who will win. Because they're all masters of their crazy deadly weapons... Like okay Manji is 'immortal', but how about we stop his movements like that, or our movements are so fast that the worms are struggling to regenarate... (you'll see by yourself in the manga) Samura's art style nearly made me a foot fetishist... I mean it opened my eyes as to why it exists. (I swear, I'm probably a 2D foot fetishist by now) OH AND I LOVED THE LANDSCAPES, maaaan it really felt like being in Japan at the Edo period!

Rapid trivia:
So yeah Masashi Kishimoto has like three inspirations for Naruto: Akira, Dragon Ball, and Blade of the Immortal. He even did an interview with Samura.
Same goes for Tatsuki Fujimoto (Fire Punch/Chainsaw Man) who is also a big fan of Samura... I guess his love for strong women was influenced by him too. x)
I SWEAR GUYS READ BLADE OF THE IMMORTAL AT LEAST FOR IS FEMALE CHARACTERS.
Samura does the most beautiful and the strongest women.

I'm pretty sure Samura was influenced by Hiromu Arakawa at least for the dreadful Habaki because its totally Bradley in our universe with samurai. (it gets even more blatant later in the last volumes) They look alike physically, they're both commanders, they have a strong will, they master in sword fighting,

Spoiler, click to view

they're interested by immortality, they seem almost inhuman at first, but they have some family struggles

I guess that's it. It was my first review, so I'm really sorry if it doesn't fit all the criterias, and if my english wasn't good enough (My main language being French, but I wanted to try releasing a review in english, to touch a larger audience because this manga deserves it). I really don't want to spoil it to people interested by it, because it is now one of my top 10 manga and I'm glad I chose to continue it rather than Vagabond (which I will continue don't worry, it's great, both are amazing samurai series but I needed a break after the Kojiro Sasaki arc, to better enjoy the rest of it).

Nonetheless, thanks for reading!