But I did see a clip in which he was coaching his son prior to Oly. I read in Miki's book that Koz's parents taught Koz in Nagoya and they went to Mrs. and Mr. Sato's near Tokyo every weekend (they brought young Miki to Mrs. & Mr. Sato's, too).
The story about Yamada and Midori is not a confirmed piece of info. But I just heard it elsewhere. And Yamada did say in a clip prior to Oly that she was in a situation where she was often seeing Mao practice and talking with her (but she did not sound like she was involved as a coach). On the other hand, Yamada has her own club in another rink. Her star student in Kanako Murakami.
I highly doubt if Yamada still wants to coach Mao again for four more years. It'd be really a lot of work to have a super star student like Mao. She could not always travel abroad with Mao even at that time.
I do not know if Midori coaches. I recall her coming back as a pro skater around 40 yrs old and trying 2A.