"Filling in the Blanks".
As with all martial arts, Shotokan karate is based on certain underlying fundamentals. These fundamentals form the "backbone" of our style and they include a wide variety of stances, blocks, strikes, and kicks, just to name a few. When used in conjunction with each other, and when properly combined with balance, posture, speed, and timing they give an experienced student a wide array of defensive and offensive combinations to choose from.
These fundamentals in turn are used to practice another mainstay of Shotokan karate called, "kata". This term refers to a series of pre-determined techniques that take place in an unchangeable pattern that must be followed from beginning to end. It is often during the practice of kata that a student first comes into contact with the term "bunkai".
The word bunkai refers to the visual demonstration of any possible application for any movement, or set of movements found within a kata. The importance of bunkai can not be stressed enough and can be introduced to students of any rank. Since it is through the practice of bunkai that students get to experience with a partner, the unseen, and in this way a kata's nature is revealed.
So, practice your kata, again and again. Learn to understand where and why bunkai fits into your training. You may be surprised at what you discover. Yes, "Karate ni sente nashi” - "there is no first strike in karate". A good defence, however, is another matter altogether.
Remember: "What you see on the surface, is not all there is to see".