TOKYO – It was inevitable that Japanese automaker Mitsubishi would seek a new capital partner. The only issue was when and, more precisely, when Chairman and CEO Osamu Masuko  felt the time was right.

The time became right in the second week of April, days before Mitsubishi would announce record fiscal 2015 earnings.

When due diligence is completed, Nissan will take a controlling 34% stake for its ¥237 billion ($2.3 billion) investment in Japan’s No.5 automaker. Nissan also will insert one of its executives as chairman, effectively replacing Masuko, who spent the past decade restructuring Mitsubishi and largely succeeding.

Masuko’s role in the new organization “will be decided by the new organization,” he tells WardsAuto in his first interview since Mitsubishi's April 20 disclosure of mileage fixing. “For the moment, my job is to lay the foundation for the alliance so that we can move forward.”

Operations by the new organization are to begin in November or December.

Masuko, a longtime critic of capital tie-ups dating back to Mitsubishi’s divorce from DaimlerChrysler a decade before, abruptly reversed course in the face of evidence the automaker had falsified fuel-economy testing data on more than 625,000 minicars sold in Japan.

A 2-month investigation revealed mileage-test results were misrepresented for 725,000 vehicles covering a range of 29 Mitsubishi and Nissan models, both 0.66L minicars and non-minis alike, dating back to 2006, the earliest year for which the automaker has records.

Masuko expresses frustration that 11 years after assuming the presidency and restructuring the automaker, literally bringing it back from the brink, he again finds himself in the embarrassing situation of having to defend misconduct inside Mitsubishi’s research organization.

“It left me speechless,” he says. “We had just begun preparations for our next medium-term business plan, and then this.”