The story of this drama is incredibly unique, at least compared to all the dramas i've seen. The Cast and Acting was terrific and as a result of both the Story and the Acting, I truly felt an emotionally attachment to the characters, and how they changed. The music also furthered my emotional attachment to the drama. While I don't like rewatching drama, Ninkyo Helper is actually a drama I believe I could rewatch, since the element of surprise enhances the story, but in general, it's not essential to making the drama interesting.
Overall, i'm giving this drama a 10, and I fell like every Jdrama fan who enjoys the Crime/Yakuza and Family genres, should watch this.