I'd like to make the suggestion that in the book, you discuss the option of ninjo and giri not being rigidly based per session. The reason isn't that I think it's a bad idea, the reason is that I think it's such a good idea that sometimes (maybe even more often than not) once a session might be too rushed. My first ninjo giri plot idea might have been a little too ambitious, and it was delayed entirely the first session because the player involved got called away five minutes before the session started. But in the second session, it had a strong payoff, everyone loved it, but we didn't actually bring it to completion in that four hours. It will come to a nice, poignant climax in the next session.
I don't know how often this will happen to me, but it might be a good idea to call this out in the text and let GM's know that it's all right, and even encouraged (if you do, indeed think it should be encouraged).