@renim as I'm not in the automotive industry it is difficult to know the complete numbers, but I can guess.
自販連のホームページ
At the bottom, on the right there are top 50 selling (standard, not Kei) cars sold in Japan in 2017. Only one EV/PHEV showed up in this list - Nissan Leaf 16.925. Other than Nissan Leaf, there are Prius PHV, i-MiEV, Outlander PHEV (probably <8000), European plug in hybrids and Tesla. In this sheet, Prius PHV is included in Prius and Outlander PHEV is also included in Outlander, and no foreign manufacturers are counted. There's a separate organization that publishes numbers but not in detail (only per manufacturer).