in the past the record was held by Ran Asakawa
in 2016 after Ai Uehara retired, beside Aki Sasaki and Rena Fukiishi; Hibiki Otsuki and Aika released new vids every months
yes
lets see who will rise in 2017
so far Nao Wakana became very active
In 2016, I would say Ayumi Shinoda was up there too