Some time has passed since Ryu Hayabusa's second adventure where he defeated Jaquio once again and stopped the Evil God from being revived. Since then he has been running a Japanese item shop with Irene Lew, the woman he met during his first adventure, and maintains a friendship with Robert T. Sturgeon, a U.S. Army agent-turned-detective he met during his second adventure. When a man named Dr. Ned Friedman reveals that he discovered a cure for cancer without any side-effects, Ryu, Irene, Robert, Jeff (Robert's partner), and Sara (a reporter and Robert's girlfriend) all become involved in a scheme to create a new superhuman race and possibly even try to revive the Evil God once again.
For those who are very familiar with the NES trilogy you can tell that this OVA takes place after Ninja Gaiden II: The Dark Sword of Chaos but before Ninja Gaiden III: The Ancient Ship of Doom; at least that's how I see it since the anime credits the second game. But this OVA does change some things about the characters that makes it a loose-adaptation and not really an potentially-canon side story. For example, Irene in this OVA is more of a doting girl who seems to have never fired a gun off, instead of being a CIA agent like she is the game series. Still, if there is one thing that this OVA does right is tell a functional story. I can see some people potentially get annoyed that this OVA isn't quite filled to the brim with action, though, since the first half is very story-based and a bit of a slow burn. The reward, though, is a very action-filled second half that should definitely please those who expect blood and violence from a Ninja Gaiden anime. Hell, this OVA should be able to please fans of the original trilogy with its use of recurring characters and fans of the reboot series with its very stylish and well-animated fight sequences, which don't shy away from showing blood, decapitations, and the like.
Even the original characters are handled pretty nicely, with Jeff being an enjoyable comedic partner in the first half before turning into a badass in the second half, and Sara is a tough and inquisitive woman who unfortunately, or fortunately, has Robert as a boyfriend, which results in some genuinely funny moments between the two. Admittedly, though, the villain is pretty simple and the "big twist" at the end is unfortunately completely hinted at in the first half, which brings down the plot a little. Still, considering how this OVA has a plot that actually makes sense, utilizes its characters in ways that work to their benefits, and has very good action in general these little complaints really don't hurt the overall product too much. I guess you could complain that the OVA treats Ryu on just about the same importance as everyone else instead of being the absolute major focus, but I feel that if Ryu was given more screen time, resulting in less development for his friends, then it simply wouldn't be as enjoyable. With this shared focus, Ryu maintains how awesome he is while Robert and Jeff get to show off their stuff as well, with Irene and Sara getting just about the most focus they should get here.
Probably a good reason why the animation flows really well and the action scenes are great are due to the director: Mamoru Kanbe, who would later go on to direct the Elfen Lied anime, Sound of the Sky/So-Ra-No-Wo-To, and the Demon Prince Enma OVA. Even though people can complain about different things regarding the Elfen Lied anime, one thing it did have was well-done scenes involving violence, and Ninja Ryukenden was probably where Kanbe was able to first show off this ability. The character designs and animation direction were done by Osamu Horiuchi, (Full Metal Panic!, Burst Angel, Ga-Rei Zero, Nadesico: Prince of Darkness),whose design style probably isn't the first thing you'd expect from a Ninja Gaiden anime, but I thought it worked well here.The music, done by Takaya Okuda (his only anime work), isn't anything you'll remember for long periods of time but it works just fine for this OVA. Overall, Ninja Ryukenden delivers from a production perspective.
The voice work is well-done, too, with Ryu being voiced by Keiichi Nanba, voice of fellow awesome video game ninja Andy Bogard from the Fatal Fury & King of Fighters series. Robert is voiced by Norio Wakamoto... Enough said. Irene was vocied by Yumi Touma, who would go on to voice Leifang from the Dead or Alive game series and Urd from Ah! My Goddess. Daisuke Gouri (Jeff), Yoshiko Sakakibara (Sara), and Unshou Ishizuka (Dr. Ned Friedman) also put in good performances, leaving you with a solid cast and nothing really feels out of place.
Ninja Ryukenden kind of surprised me in how enjoyable it was. It seems like a lot of people don't know that there is an anime based on the Ninja Gaiden series, and the general reception I have seen for it seemed to be mixed. I really can't see why, though, since it delivers a very well-produced and enjoyable anime based on a video game and it really makes me wonder why it wasn't licensed back during the mid-to-late-90s. Since there isn't a DVD release of the OVA there's little chance of it ever being licensed, but this is definitely a cool title to hunt down and watch. While titles like the previously mentioned Tekken, Samurai Shodown, & Panzer Dragoon made people feel that anime based on video games would always suck back then titles like this were ignored. It kind of just boggles the mind, honestly.