Final answer:
The most popular form of Buddhism in early Japan was Zen Buddhism, which focuses on achieving enlightenment through meditation and self-discipline.
Step-by-step explanation:
The most popular sect of Buddhism in early Japan was Zen Buddhism, which teaches that enlightenment comes through self-discipline and meditation. Zen Buddhism, also known as Chan Buddhism in China, emphasizes the disciplined practice of meditation similar to the austere and monastic characteristics found in the practices of a Chan master. This form of Buddhism became widely practiced in Japan, stressing the importance of meditation and following the example of masters who underwent great hardships to achieve enlightenment. Zen is a branch of the greater Mahayana Buddhism tradition, distinct from other forms like Pure Land Buddhism, which focuses on devotion to a savior being for salvation.