Yanagida's manager Ted McLachlan was at Waikato Hospital with the jockey during his initial assessment and was among those left stunned by the fall.
"Taiki arrived here [around 7pm] and was taken straight to the ICU in an induced coma," said McLachlan.
He said it "could be four or five days before we know the extent of his head injuries."
Yanagida has been a big mover in the northern jockey ranks in the last two years and had a personal best season last term with 42 winners in his first year out of his apprenticeship.
He was born and raised in Japan, where his parents still live there. They don't fluent speak English so are being kept updated on Taiki's condition by fellow Japanese jockey Yuto Kumagai, who like Yanagida is also now riding in Waikato.
Yanagida's parents are expected to fly to New Zealand, arriving on Friday morning to be with their son. New Zealand Thoroughbred Racing chief executive Bruce Sharrock has confirmed NZTR will pay for their flights.