Embusen (演武線) is a Japanese term used in karate to refer to the spot where a kata begins, as well as its line of movement. Nearly all kata start and end on exactly the same embusen point. This word is also commonly romanized as enbusen.
The embusen line varies for each series of kata. It is, for example, a straight line for the Shōtōkan Tekki series of kata. It follows the form of a capital letter I for the Heian series of kata, as well as for the Taikyoku series. More advanced kata, such as Shotokan's Kankū-dai and Gojūshiho dai kata, as well as the Gōjū-ryū Seipai and Kararumfa kata, for example, have increasingly more complex embusen to train the practitioner in more advanced defensive angles and footwork. For any kata, the embusen is fixed and must be followed exactly for proper mastery of the style.
While many attempts over the decades (and the centuries) have been made to document most fighting styles, the bulk of the training is best taught person-to-person, and most of the details are taught orally. The experienced practitioner should find this to be a well-balanced explanation of the term embusen.