In upanishads guru means remover of darkness. Only you can remove the
darkness in you by efforts and focus. The movement you see light
within you, your darkness is removed. It does not attribute any
individual particularly. You will never have a guru other than whats
within your heart. There are many forms and names out there who could
help you find the supreme self or guru within you. If you call any
human as guru, for one with higher level of conciousness its simply a
name and efforts of them are karma.