The strength and weakness of this series is its single-minded righteousness.
The cruelty of a cult is that most of the are desperate victims. In other words, it's hard to make them threatening and unsympathetic. The artist/author only has three characters with ANY chance of injuring Kiku: Gin, Mudo, Gatchan. Gin was lied to and questions it in the last second of her life, Mudo was a fellow victim on Kiku's side all along, and Gatchan is just a helpless mindless prisoner being used like a mule. The cult doesn't have a single serious fighter who truly understands and defends Aiichiro!
Mudo comes the closest - but it turns out that he shares Kiku's motives all along. So why didn't he set up a private meeting and explain the situation so they could fight side-by-side? Instead they get in a pointless deathmatch which ends with Kiku destroying his only ally in the church.
Speaking of allies, what happened to the woman helping him out at the beginning? She seemed cool, but she takes off after witnessing Kiku's arrest and we never see her again. I guess there was no opportunity to bring her back, but then why was she there in the first place? Just to let Kiku humanize himself by hesitating to kill Gin? Kiku never has to fight another elderly person, so it never needs to come up again.
When Mudo dies, Kiku no longer has any opposition. He effortlessly gets inside the compound and kills Aiichiro in front of his followers and, surprisingly, that's it. What happens to the church? Their leader was decapitated in front of the entire world! He was just about to meet up with the prime minister! It feels very perfunctory - wasn't this mission Kiku's only reason to live? He should either die in the process, or find something that redeems him (like love to go on living), but all the kind characters are driven off or killed. Saruwatari doesn't give Kiku death or love. Only victory. But is it still victory if we don't see the church actually collapse, and have to assume it does? Is Kiku capable of becoming a happy person, or is he just going to kill himself off-screen?
The stuff I'm nitpicking might sound dissatisfying, but it's all forgivable because the story is very clearly not the point. This manga is about evil cultist sickos getting their body parts rearranged. Kiku can't be anything but an invincible avenger because that's just how perverse his environment is. But unlike the other reviewers, I find him charming and likable. A helpless crybaby corrupted by a sick world into a killing machine, possessing only monstrous strength and a morsel of comion - what more do you need in a fighting seinen? The part I knew I would like this manga is when the dying man whose family was killed by the cult begs Kiku to kill him, and Kiku breaks his neck, but not before hugging him.
Dokuro is a very honest story. There is no pseudo-sophisticated high-concept twist like "fighting against evil makes YOU the real evil!" or "religions can never be destroyed because the church will survive the death of its constituents". This is a story about a guy single-handedly ending a fake religion with the blessing of God. You can feel the author gritting his teeth. He wants to see evil people get torn to bits for the victims they've destroyed, but it can only happen on these pages.
As far as the fights go, they're excellent abrupt bloodbaths in the Hokuto no Ken style - big evil fuckers mouth off and our unsmiling hero punches straight through them. If you liked Riki-Oh (illustrated by the same magnificent artist), definitely check this out. At 4 volumes, Dokuro is a super-quick read. You can get through the whole thing in an afternoon.
