By Sam Nussey and Ritsuko Shimizu

The companies are looking at a range of opportunities beyond convenience stores, said Koji Takayanagi, previously head of the food division at trading house Itochu Corp.

FamilyMart UNY Holdings, formed from the merger with Uny Group to become the second biggest convenience store chain behind Seven & i Holdings Co, has forecast operating profit to grow to more than double to 100 billion yen ($901.39 million) in four years from 41.2 billion yen in the current fiscal year.

This will be driven by converting its Circle K and Sunkus stores into more profitable FamilyMart ones, increasing stores sales by 10-15 percent, Takayanagi said.

"There is plenty of room for growth," he said of the company, which also runs supermarkets and general stores.

While FamilyMart is profitable in Taiwan and China, it is reviewing its loss-making businesses in Thailand, Vietnam and Indonesia. "If we can get them to rally we will, but we cannot continue to pour in resources," Takayanagi said.

While its rival Seven & i Holdings, which owns Japan's largest convenience store chain 7-Eleven, expands overseas, most recently in the United States, FamilyMart will remain focused on the domestic market, Takayanagi said.

"It is easier to achieve results domestically and we know what we need to do," he said.

Japan's worsening labor shortage, which is leaving convenience stores scrambling to find workers to man tills and stack shelves, will force companies to adapt and innovate, he said.

Even the country's declining birthrate and aging population does not phase Takayanagi.

"Even if the amount an individual eats declines... if we offer items with added value people will buy them."

(Reporting by Sam Nussey and Ritsuko Shimizu, editing by Louise Heavens)