SINGAPORE — Brandon Vera was recently pinned in a corner by an excited mob at a shopping mall in the Philippines, and briefly thought that he might have to fight his way out. But instead of brandishing weapons, the crowd was armed with pens and cellphones, hoping to get autographs and selfies with Vera, one of Asia’s most popular mixed martial arts fighters.

The incident is a common occurrence for Asian celebrities as varied as athletes and actors and Korean boy bands, but Vera’s presence at the center of a fan frenzy made it different: he is an American, a former college wrestler from Norfolk, Va., who moved to his ancestral homeland three months ago, ahead of the first defense of his mixed martial arts heavyweight title, which he won in December in the Philippines.

“It’s been overwhelming, wondering why I get so much attention,” Vera, 38, who fights for ONE Championship, Asia’s largest mixed martial arts promoter, said at a recent M.M.A. function in Singapore. “And most of the time I’m thinking, Whoa, whoa — what’s going on here? Honestly, that is the question that goes through my head every day.”