TOKYO—Sanrio shares tumbled as much as 20 percent on Monday, the company's largest single-day decline in over 12 years, after first-quarter operating income missed analyst consensus estimates.

The Hello Kitty owner reported 22.4 billion yen, or U.S.$141 million, in operating income for the first quarter—1 billion yen below the Bloomberg consensus estimate of 23.4 billion yen.

The drop erased a large portion of Sanrio's prior gains. Shares had risen almost 50 percent since Jan. 1, 2026, outperforming the broader Topix index during that period.

Kazuhiro Sasaki, head of research at Phillip Securities, attributed the sell-off to investor behavior. Shares had been rising rapidly since late June, he said, prompting many investors to sell once the report offered no positive surprises.

Morgan Stanley MUFG analysts Katsumi Arai and Akiho Toyama offered a mixed outlook. They said the first-quarter results could prompt near-term profit-taking and weakness, but saw no need for major concern as the business progresses steadily.

Prior to the earnings announcement, Sanrio traded at a trailing price-to-earnings multiple of 25 times—the company's lowest multiple in over 10 years.