Recently I saw "The Time Tunnel" (2002) Unaired Pilot on YouTube (the series did not get made.) It reminded me of a TV series I saw maybe in the last 10-15 years.
I remember little of it, other than it seems to have a small cast, maybe with an Asian male lead. Maybe set in San Francisco. (Maybe it was set elsewhere and just in one of the first episodes he went to San Francisco.)
Unfortunately I remember little else of the series.
It might've been Moon Bloodgood). Pretty small recurring cast from what I remember; besides the two of them, I'm pretty sure the only other regular characters were Dan's wife and brother.
The intro was pretty memorable too, it might kick some memories if it was.
Maybe Quantum Leap (2022) ?
A sequel to the 1989 series of the same name, with an all new cast and characters.
The lead character is played by Raymond Lee, an Asian-American actor of Korean descent.
Thirty years have passed since Dr. Samuel "Sam" Beckett vanished into the Quantum Leap accelerator. The United States Department of Defense has restarted the Quantum Leap project with a new team trying to recreate the accelerator and retrieve Beckett from the past. For reasons unknown, Dr. Ben Song, the new project's lead physicist, has uploaded new program code to Ziggy, the project's supercomputer and used the upgraded accelerator to leap back in time without informing anyone on the team as to why. He becomes stuck in the past just as Beckett did, living the lives of other people and changing history for the better. However, his leaps appear to have a trajectory to take him to a specific point in spacetime. Project employee Addison Augustine, who is Ben's fiancée, acts as his liaison with the project, appearing to him as a hologram that only he can see and hear, just as the previous project's observer Al Calavicci did for Beckett.
The nearly forgotten Journeyman TV show from 2007 featured time travel as a core story element, was set in San Francisco, and had an Asian lead actress (Moon Bloodgood).
Perhaps this is "Heroes", which was on TV during 2006-2010. One of the lead characters is Hiro Nakamura, an office worker who can manipulate space-time. He is played by Masi Oka.
There was indeed a small cast of about a dozen actors. The series is notable (for me) for the slogan "Save the cheerleader, save the world" which refers to the prediction that Claire Bennet, a cheerleader played by Hayden Panettiere, is predicted to somehow prevent an event that will cause global destruction.
Depending on how many details you can't remember, could it be The Man in the High Castle?
In a dystopian America dominated by Nazi Germany and Imperial Japan, a young woman discovers a mysterious film that may hold the key to toppling the totalitarian regimes.
It involves travel between parallel universes, much of it takes place in San Francisco, and there are a number of important Asian characters. This one is a bit of a stretch, because you didn't mention the conspicuous Nazi occupation of the Eastern US, but I believe there were some episodes that mostly focused on the West Coast, so you may have missed that.
Here are two central characters living in Japanese-occupied San Francisco:
Sliders
If it was set in San Francisco, I think Sliders might be it. Not a time travel show but alternate dimensions, where the main characters have to jump from timeline to timeline after a physics experiment goes wrong. These timeline jumps frequently look like they've gone to different times. For example, in one episode they go to a time where dinosaurs never went extinct, a couple with medieval themes and so on. The characters are trying to get back to "their" San Francisco, and multiple episodes deal with them arriving in a San Francisco close to normal but with one specific difference. One episode cops wear skirts because of Hoover but the city seems similar, another the golden gate bridge is a different color but everything else is identical, that sort of thing.
None of the recurring cast was Asian, but here's a picture of the two lead actors from the first few seasons, John Rhys-Davis, who played Dr. Maximillian Arturo and Jerry O'Connell, who played Quinn Mallory
