If this film came out in the 80s it would have been right up there with the American Ninja series. This is not a slight on Scott Adkins, as I think he is phenomenal talent in martial arts. There was just something missing for me in this film. All the ingredients seemed to be there. They had a lead man (Adkins) who looks and makes the part. There was just something miss for me. The film just seemed a little dated for me.
Adkins is brought up in a Ninja training school in japan. Being the only westerner he has to work harder then everyone else to earn his place there. The head boy (or best student) takes and instant dislike to him. Partly seeing him as a rival, and partly because of the attraction between Adkins and the Sensei's daughter. Not being able to control his anger at Adkins get him thrown out of the school, when he is over aggressive and uses a real sword in a sparring match.
After doing thrown out this student become more high tech version of a Ninja assassin. Complete with body armour and night vision goggles. He still uses ninja stars, but replaces the more traditional bow and arrows with guns (good choice). Yet he still wants what he feels was his, the traditional Ninja amour kept in a box in the dojo. Making his intentions know to take it by force. The box is moved to America. Adkin and the sensei's daughter are sent to guard it. Now the battle spills over to America. Complete with an evil cult of evil oil barons, with their own agenda.
Huge gore factor in this film. Absolute fountains of blood, after slashes or gunshots. The martial arts are great acrobatic displays, but the filming does look dated. If it was made in 30 years ago even with a fraction of the budget it would have been a block buster. The film was just ok for me nothing special.