I'm not entirely sure what to make of this film--I suspect I need to view it at least once, and probably several more times before I can get a good hold on it. However, my inability to fully comprehend what "Sonatine" is about doesn't strike me as a flaw. Rather, the film is much more complicated than the usual gangster film.
It begins with very unsentimentalized and nonglorified violence. People hit and kill each other and it isn't much different than toast popping out of the toaster. It is fast, moderately bloody, and there. Kitano doesn't seem to be interested in thrilling us with either the danger, grotesqueness, or thrill of violence--another, not clearly defined agenda is at work here.
At perhaps a third of the way into the film, it makes a sudden transition from this gangster life to a period of forced inactivity. I suspect this section, which is delightfully playful, is at the heart of this film.