The premise in itself is unique, as almost all historical manga take place in at least the Sengoku period onward. Despite the lack of surviving information on that time period, you can really author has really did his research, as evident through the setting and art staying relatively true to contmeporary lifestyle, the help he's gotten and the tidbits at the end of every volume (available if you purchase physical copies of the manga or digitally on the official Viz website!!!). Despite the manga's attempt to be as true to history as possible, it is important to keep in mind that The Elusive Samurai is still a work of entertainment first and foremost and therefore has taken a lot of liberties in its loose re-telling, which gets looser as time goes on. Like, I'm talking about the existence of divine figures and even ridiculous machinations. It's also over-the-top in its depiction of historical figures and action, as well as conjectures about historical omissions, to the point where it's not only absurd but also boring. Think Romance of the Three Kingdom's flaws, notably where most battles are decided through exaggerated strategies or legendary-like heroes, and crank that up to 11.
So, The Elusive Samurai isn't exactly compelling in its historical aspect. Is it an amazing comedy adventure manga, then? Ehhhh. The manga's biggest flaw, if you don't consider its far-fetched fictionalisation of historical events one, is its humour. The manga has established the end of the Kamakura period to be extremely chaotic, brutal with vile acts against humanity strewn about Japan - its perpetrators to be cold-blooded, inhumane, hell even literally inhuman. It's why whenever the manga focuses on Tokiyuki having kid-like interactions with his friends and loved ones, which is probably for many this manga's selling point, does everything feel so... surreal. You got kids hanging around murdered and multilated innocents, killing dozens of villians and a couple of pages later they're playing tag or something. It's truly bizzare. I'm always taken out of my immersion whenever this stark contrast comes up. Sometimes, the nonchalant scenes just feels like the author's having his cake (drawing underaged characters in obscene situations) and eating it too. And the author wants a lot of cakes. Although, you can and should argue that this jarringness is a byproduct of the period - after all, it is true that many children not only regularly lived through such turbulent periods, but even thrived in them (some even appearing in the manga and having their seemingly insane exploits acknowledged!)... but I would have personally loved if the manga was a little bit more grounded. Seeing so much gore and brutality of people gets old after a while... and that's not a good thing!
Even after all that, I probably wouldn't have this manga any other way. Its bizarreness is what makes it stands out, keeps the story coherent and enjoyable to read, after all. In that aspect - making a story people want to read and love to keep reading, while learning new things in the process - is what Yusei Matsui's insanely good at.
I just realised I don't really have any opinion about the characters and character development because honestly they're all kinda surface-level. Which is funny, since that's what all non-history-defining pasts figures are anyway for us in the present