BEIJING, Dec. 29 (Xinhua) -- Domestic thriller film "Fireflies in the Sun" stayed atop the Chinese mainland box office chart on Tuesday, data from the China Movie Data Information Network showed Wednesday.

The movie, which is a sequel to "Sheep Without a Shepherd" released in 2019, depicts the story of a poor family and a desperate father who gives all his efforts to collect money for his son's operation.

On the 12th day of its release, the movie raked in about 22.4 million yuan (around 3.5 million U.S. dollars), accounting for nearly half of the day's total.

"B for Busy," a domestic romance movie, ranked second on the box office chart, raking in 10.5 million yuan on its fifth day of release.

It was followed by animation "I am What I am," whose daily box office earnings were close to 4 million yuan. Enditem