Matsumura could not be reached for comment. But a statement from Ramen Underground on Facebook cited a waning clientele due to COVID-19 as the reason for the closures, which they attempted to combat in part by selling their bento boxes for takeout online.

“We would like to say thank you for all customers with us,” the statement continued. “Really sad to say bye (to) all of you.”

Matsumura previously worked for the bustling Union Square ramen joint Katana Ya before deciding to pursue his own restaurant venture. Ramen Underground was named a Readers’ Choice Winner by the San Francisco Examiner in 2018.

“Breaks my heart to know that you’ve put your heart and soul into this business for so long and now it’s closing,” one customer wrote in response to the statement. “I’m really sorry to hear that all of this is happening,”

In 2012, shortly after Ramen Underground opened to the public, San Francisco resident Victor Wong told the Wall Street Journal he ate there at least every other week. Yet, like many fans of the restaurant, he was puzzled by its name, which didn’t seem to reflect its burgeoning popularity. “They do one thing and they do it well,” he said.

The dual closure follows a pattern of downtown restaurant losses after their target clientele – tourists, convention crowds and people working in the area – abruptly disappeared this March.

M.Y. China, a restaurant owned by celebrity chef Martin Yan, also closed at the end of November following 10 years of operation at Westfield San Francisco Centre. Yan told SFGATE his restaurant’s location on the fourth floor of the mall made its survival particularly challenging.

“Nobody is going to go up there,” he said. “Most takeout restaurants can only survive and do takeout on the ground level. There’s no sense to open because there's no revenue."

Yet, like Yan, the staff at Ramen Underground and Udon Underground also feel optimistic that they will be able to reopen again someday:

“Hope we can see you in the future when we return,” they wrote.

SFGATE Food + Drink Reporter Susana Guerrero contributed to this report.