A Chinese indie film about emigrants from southern Guangdong province’s Chaoshan region, and filmed almost entirely in the local Chaoshan dialect, has become an unexpected hit at the domestic box office.

“Dear You,” of which the Chinese title translates to “Love Letters to Grandma,” premiered on April 30 in Chaoshan, before gaining national attention this week. The film has earned a total box office revenue of 143 million ($19 million) as of Monday and is expected to reach 300 million yuan by the end of its theatrical run on June 11, according to ticketing platform Maoyan.

The film has racked up a sky-high average rating of 9.1 on the Chinese review platform Douban — the highest among all films screened in China so far this year.

Featuring a largely novice cast, the drama begins in the 1940s and tells the story of a Chaoshan family from the perspective of the family’s grandson. The family’s matriarch, Ye Shurou, is left to raise three children alone after her husband, Zheng Musheng, joins millions of others from the region who emigrated to Southeast Asia in search of work and opportunities — a historical event known as xia nanyang, or “going down to the Southern Seas.”

Central to the story are qiaopi — letters and remittances sent by emigrants back to their families in the 19th and 20th centuries, serving as both a vital source of income and a spiritual lifeline. The practice was added to UNESCO’s Memory of the World Register in 2013.