It starts off pretty strong, with great animation, if a bit cliche - you know what's coming from a mile away if you've ever watched some shows before. From there, it ramps up into a gritty show that slowly builds up its story and holds the mark...
But here come the 'but's. First of all, the starting holds absolutely no meaning, because having his kid get murdered too is completely pointless - we've not known the character, his wife nor kid for any amount of time, and having his wife get killed would have the same impact, not to mention there's absolutely no introduction scenes to the kid in the show... It would make much more sense to hold onto the reason for his revenge until much later, and instead of the kid use the time to flesh out the relationship between him and his wife more as the series progresses and we get to know MC more, THEN hit the viewer with her murder.
Secondly, around the mid point, the quality takes a huge dip, be it because of the tonal shift from ninja arts and normal fights to sci fi and robots, the shitty cgi used for said robots either due to budget cuts or the need for it because they wanted to differentiate them from normal fights, or both..
And lastly the story, that is basically not revealed until the last third of the show, and turns out to be downright pathetic. There's basically three main silly little stories :
1, MC's, who's the simplest and stupidest, and i'd consider a substory - bla bla, ninja code says you can't love and have friends, bla bla, he fell in love anyway and got a friend, bla bla, he ran away into hiding, had a kid, and then he, his kid, and wife got murdered for having a family and leaving the clan, but he has an immortality 'ninja art' and now is on his revenge that he gets by the end
2, his friend, that's also basically a sub story - basically he also broke the code by being friends with MC and his wife, and they swore to be friends and stuff, but then ran away and left him behind. And he decides to kill MC, cuz he feels betrayed and his friend broke the clan law and other utterly idiotic reasons, but in the end decides to help MC
And 3, which is actually the MAIN but also LEAST fleshed out story - just a medic war veteran who saw too much horrors and decided to take over the world and FORCE peace lol, because that's DEFINTELY how things work! And for that he needed robots..? Idk, this part, like most things in the show doesn't make sense, as these robots aren't shown to be all that special, and the fights in them, if anything, look far weaker and slower than the normal ninja fights.. Also the NORMAL ninjas look more than overpowered enough to take on the world leaders as per bad guy's plan.
This gives birth to more utterly redundant characters and subplots such as the useless Aryan looking Mark Zuckerburg evil CEO type that makes the robot stuff and his bodyguard Ninja that the Villain assigned to him and told her to protect, but then decided to kill because she FOLLOWED HIS ORDER and he didn't cancel it! (Utter lunacy), the bunch of baddie's henchmen that don't even deserve a mention with how idiotic they are (mc's firend one of them), and the near pensioner policeman along with his sidekick (new poliecegirl recruit who's a double agent) who was probably the best character in the show as far as her plot, story, fleshing out, and reasoning goes, but who got killed off for absolutely no good reason.
Final score - 5.4/10, just for the art of the first episodes, probably not recommended, unless you really like ninja stuff and don't mind stupid plots. And even then you'll hate the robot fights.
Frankly, i'd say it could have been a good show if they cut half the characters and the silly robot stuff, and the runtime to 6x30 or 6x40 min episodes instead of 13x24 min, but alas.
