There were many Sapa Incas. Some are called the Lords of Cuzco. These were the kings who ruled the Inca people before they became an empire. There is no proof that the Lords ever existed. They may be simply legend. Manco Capac was the mythical first king.
Some are called the Emperors of the Four Quarters. These emperors, or Sapa Incas, probably really existed. The first was Pachacuti.
Today, school kids in Peru recite all the Lords and all the Emperors in a chant.