The Prison arc is over.
The last two volumes have gone a good way in redeeming the tedium. After tracing the manga's "horror" roots from the beginning, Samura also recalls one of his greatest strengths, delivering one cinematic action sequence after another. The most desperate confrontation -- against a seemingly perfected immortal as the greatest results of Brando's experiments -- ends in one of Samura's trademark two-page spreads. And the epilogue provides a fitting, almost feel-good wind down as characters reunite, stronger than before.
That is, if anything, the strongest argument in favor of the arc. While having the main character stuck in a cell for months doesn't allow any excitement, Rin sees a massive growth during these volumes that shows the kind of indepedence and convinction that many readers would think impossible of her at the start of the story. Doa and Isaku also gradually become very human characters, and the backbone for plot development; even Hyakurin and Giichi find internal resolutions before the end.
Outside of the likely involvement of Ittō-ryū and the ever-psychotic Shira, I've no idea where Samura has taken Blade of the Immortal in Japan. Still, for the first time in years for English readers, the narrative is wide open again.