When Ricky Phung tried to get Sharon Zhen’s attention by tripping her in the ninth grade at San Gabriel High School in California, he was unaware that she had already fallen for him.

“I thought she was cute and I really liked her, but I didn’t know how to approach her,” said Mr. Phung, a 29-year-old marketing manager at Faraday Future, a company in Los Angeles that plans to manufacture electric cars.

“I spent a year and a half trying to figure out a way to introduce myself,” he said, laughing as he recalled that moment in 2000 when Ms. Zhen tumbled to the floor and into his world.

“After all that time,” he said, “I still didn’t have much of a plan.”

The task of meeting Ms. Zhen, which soon became Mr. Phung’s most difficult high school project, had begun the year before at Richard Garvey Intermediate School in Rosemead, Calif., where Ms. Zhen enrolled in the eighth grade shortly after her family moved from Los Angeles.