Chief Executive Officer (CEO) Masatsu Nagato, and the heads of the postal and insurance branches, Kunio Yokoyama and Mitsuhiko Uehira, respectively, had already announced their decision to the others on the board.
Executives will assume responsibility for a fraudulent insurance and financial services sales scandal that affected thousands of clients, most of them elderly, Efe news reported.
Authorities have opened an investigation into the conglomerate, heir of the former state postal and banking services company Japan Post, which has been controlled mostly by the state since its IPO in 2015.
The scandal of abusive practices by commercials trying to meet the ambitious sales targets came to light after an internal investigation following numerous complaints filed by customers.
The company detected around 183,000 cases of irregular charges to elderly clients between 2014 and 2018, consisting of unnecessary modifications to their contracts or repeated charges for the same service, according to Kyodo News data.
Conglomerate executives offered a press conference on the 18th to apologize to the affected customers, and in it the CEO of the group said "he would make an announcement about the responsibilities of the managers when the appropriate time came."
After knowing the impending departure of managers, the conglomerate matrix - and tenth company with the largest capitalization of the Tokyo Stock Exchange - Japan Post Holdings - ended Wednesday's trade with a 0.73 per cent decline in shares in the Tokyo market.
Its banking and insurance branches also suffered 0.86 per cent and 1.14 per cent falls, respectively.
( With inputs from IANS )