An important sacred text of the Japanese Tachikawa school is the Sutra of Secret Bliss (ca. 1100), the full title of which is Sutra Proclaiming the Secret Method Enabling a Man and a Woman to Experience the Bliss of Buddhahood in this Very Body. This sutra contains the school's general teachings concerning sexuality and its role in reaching enlightenment.
Apart from such specific terminology, this and other texts clearly demonstrate the deeply sexual orientation of the Tachikawa adepts in their choice of other words related to sexuality.
Not only do they use flowery, romantic and secret language for the genitals, but also for the various sexual positions, secretions, and parts of the body:
The Sutra of Secret Bliss and most other texts of the school, for example the Yugikyo (Yoga Sutra), Yoshinshu, Sangai Isshinki and Hokyoshu Sangen Menju, date back to the 12th and 13th century; after which the school was outlawed and had to go underground.