The term "Esoteric Japanese Buddhism" refers to a unique branch of Buddhism that developed in Japan during the 9th century. It is also known as Shingon, which means "True Word" or "Mantra." This form of Buddhism is based on the teachings of the Indian monk Kukai, also known as Kobo Daishi, who traveled to China to study the esoteric teachings of Vajrayana Buddhism.

Esoteric Japanese Buddhism is characterized by its emphasis on secret teachings and practices, which are only revealed to a select few initiates. These teachings are believed to have been passed down from the historical Buddha, Shakyamuni, to his disciple Vajrasattva, and then to Kukai. The goal of these teachings is to achieve enlightenment in one's current lifetime, rather than in future rebirths.

One of the key practices in Esoteric Japanese Buddhism is the use of mantras, which are sacred sounds or phrases that are believed to have spiritual power. These mantras are chanted or recited during meditation as a means of purifying the mind and attaining enlightenment. The most important mantra in Shingon Buddhism is the "Dainichi Nyorai" mantra, which is associated with the cosmic Buddha, Mahavairocana.

Another important aspect of Esoteric Japanese Buddhism is the use of mudras, or hand gestures, and mandalas, or sacred diagrams, which are believed to have spiritual significance and help practitioners focus their minds during meditation. These practices are also used in rituals and ceremonies, which are an integral part of Shingon Buddhism.

Esoteric Japanese Buddhism also incorporates elements of Taoism and Shintoism, the indigenous religion of Japan. This can be seen in the use of nature and natural elements in rituals and ceremonies, as well as the incorporation of local deities and spirits into the Buddhist pantheon.

In addition to its emphasis on secret teachings and practices, Esoteric Japanese Buddhism also places a strong emphasis on the relationship between the teacher and student. The teacher, or guru, is seen as essential for transmitting the esoteric teachings and guiding the student on their path to enlightenment.

In conclusion, Esoteric Japanese Buddhism, or Shingon, is a unique form of Buddhism that combines elements of Vajrayana Buddhism, Taoism, and Shintoism. Its emphasis on secret teachings and practices, as well as the importance of the teacher-student relationship, make it a distinct and fascinating branch of Buddhism.