Salvia nipponica should be a lot like S. glutinosa, S. koyamae, and S. nubicola, to which it is related. It may take more than the usual 10 - 14 days to germinate. I would keep the seed bed at a temperature of 70 degrees F at least, maybe 80 degrees, sow it on top of the seed flat with a light dusting of milled spaghnum or some other fine sterile germination media. By next morning, the gelatinous seed coat should swell up.