Japan Airport Terminal President Nobuaki Yokota and Chairman Isao Takashiro resigned Friday amid a corruption scandal involving the operating company for Tokyo's Haneda Airport terminals and a son of Makoto Koga, former secretary-general of the ruling Liberal Democratic Party.

The company said it accepted resignation offers from the two top executives the same day.

They stepped down as Japan Airport Terminal's Audit and Supervisory Committee was investigating allegations that the company had illegally benefitted via a subsidiary of a consultant firm headed by Koga's first son in the massage chair business at terminal buildings of the airport.

Specifically, the Tokyo-based Big Wing unit paid the consultant firm about ¥100 million, in total, over five years through March 2016 as commission fees for the massage chair operation, although actual work was undertaken by another company, people familiar with the matter said.

In a related development, the Tokyo Regional Taxation Bureau has concluded that the consultant firm is a shell and that Big Wing's payment to it amounts to income concealment. The Koga-linked firm was also found to have failed to declare commission fees it received directly and indirectly from Big Wing as taxable income and was slapped with about ¥40 million in penalty taxes.

Japan Airport Terminal will announce a new management team shortly. It also plans to disclose the results of the investigation after reporting them to the transport ministry.

After joining the Haneda terminal operator company in 1974, Yokota became president in June 2016. Takashiro, who entered the firm in 1968, assumed the post of chairman in June 2016 after serving as president since 2005.