After teaching him the wisdom of Esoteric Buddhism, copies of the sutras were made to be smuggled out of China. “While hiding out on a mountain by the sea, Master Kukai threw the three-pronged vajra toward the waters.” Master Kukai couldn’t go straight back into the capital because he faced punishment for early return from the Tang. While hiding out on a mountain by the sea, Master Kukai threw the three-pronged vajra toward the waters. Turns out it is from China, where Master Kukai learned everything about Esoteric Buddhism.