In the future, people live in a world of ruins and magic, and everyone is looking for certain relics from a civilization past — O-Parts, items which when used properly and by the right person can release power of epic proportions. Only O.P.T.s — O-Parts Tacticians — can use O-Parts, and not all of them are the good guys . . . Enter Jio, a young boy with a dark past who has only one goal: conquer the world! He's an O.P.T. with the most frightening alter ego of all – Satan! Together with his treasure hunter companion, a girl named Ruby, Jio travels the world to find O-Parts, only to get caught up in a war with the evil organization Zenom, which also wishes to take over the world by using all of the O-Parts and completing the Kabbalah and Reverse Kabbalah, weapons of immense power that could destroy everything.

Highlights:

The final volume of O-Parts Hunter opens with Ball and the others (minus Jin and Zero) entering the heart of Zenom's lair, accompanied by enemy-turned-ally Spica, who is now loyal only to Futomomotaro. Meanwhile, Jin and Zero take out an enormous octopus who is proving more formidable that he imagined. The main party confronts Zenom, and confirm their worst fear: Zenom is, in fact, Ruby's father once thought dead. He acts as if he never had a daughter, which sets off the others to start fighting. Before anything can start, Zenom grabs Cross and takes him on top of Lilith's Sephirah Number 91 on the Reverse Kabbalah to leave him there while he takes care of the others. He reveals he has the legendary O-Part, then his soldier Baku attacks the group using his illusions — until Jin and Zero crash the fight. They take on Zenom, but with no success as Zenom snatches away his demon core, revealing his true powers in the process. Zenom summons both Asmodeus and Belphegor to attack the group with darkness data, but his attack is cut off by the appearance of Jio

Chapter two cuts away from the action briefly with a flashback to the day Ruby's father left and never came back. The story resumes with Jio and friends battling Zenom head on, a clash of O-Parts against O-Parts. In the struggle, Baku somehow grabs the legendary O-Part and reveals his true identity of Amaterasu Miko. In the lull of battle, Ruby demands of Zenom to acknowledge that he is her father, and the uneasy truth is revealed of her true lineage, as well as revealing Zenom's amnesia surrounding his past. As forces move together, both Reverse Kabbalah and the Kabbalah are merged to create the ultimate weapon, with its intent being Armageddon. The final battle begins as the new creation, Shin, begins absorbing both humans and recipes at an astonishing rate, including Ruby and Jio. Inside Shin, Jio battles the heart of the machine.

As Armageddon itself looms over the horizon, Jio finds that he'll not only have to defeat the combined Kabbalahs to save the world, but also the demon lurking inside of him — the beast Satan! Will Jio succeed in his battle against his own inner self or will the world of O-Parts come to an end?

Overall:

Do not compare Seishi Kishimoto's O-Parts Hunter to his brother's more popular work; you will find few similarities. In fact, it triumphs over his brother's premiere work in one major way: it ends. And what an ending it is. Any shonen fan who has been following the series so far will not finish this book disappointed: it holds epic battles and stunning revelations aplenty, the kind that makes the series so one-of-a-kind. It doesn't take a genius to make a "gotta catch 'em all!" type manga series; it takes a certain kind of manga-ka to create one that holds enough twists and turns to make it something remarkable. Jio Freed is a compelling character himself: headstrong and carefree, born from a tragic past and destined to live alone — and yet, at the end of the series, he has made himself an unorthodox family of allies and loved ones from his travels to conquer the world.

Kishimoto's art is bold and fluid; the action scenes move quickly across the page, and his flashbacks are some of the better ones in current shonen series. Jio and his female companion Ruby are supported by a cast of secondary characters, all with distinctive personalities and lives of their own that flesh out the O-Parts verse, although some readers may be miffed by the fact that not everyone's story lines is wrapped up as neatly as they'd like by the end, not to mention the ending may be polarizing to those more emotionally invested in the fate of our beloved main characters. Still, this will not disappoint its long-term fans as it ends a great series not with a whimper but with a loud and satisfying bang.

ComicsOnline gives O-Parts Hunter volume nineteen 4 out of 5 legendary O-Parts