Almost a year later than first expected, Apple finally added indoor maps for Japan. Narita Airport and Chubu Airport are the kickoff points for what is hopefully going to be a continuous rollout. Major airports like Haneda and stations such as Tokyo and Shinjuku are still MIA and the iOS Feature Availability list has not been updated yet.
One of the problems that Apple Maps faces in Japan is that multiple agencies hold different indoor map data sources. Coordinating a complete robust data set takes time.
(Via Ata Distance)