A group founded to promote the use of Cantonese in Hong Kong has shut down after authorities raided its founder's family home last week.
The government cited the controversial national security law and asked the foundation to take down a three-year-old short story.
The raid is seen as another erosion of freedom of expression in the city.
The group's founder told the BBC that he decided to shut down the organisation on legal advice.
"My biggest concern is the safety of my family members and friends in Hong Kong. I found out that if I did not shut down the organisation, they could keep using the materials online, and harass the people I care about," said Andrew Chan, 28, who teaches Chinese and Cantonese online.
Cantonese is a Chinese dialect spoken by an overwhelming majority of people on the island, as well as the Guangdong province in China.
Mr Chan founded the Hong Kong Language Learning Association with the mission to protect the "language rights of the Hong Kong people".
Flashpoints between Hong Kong and mainland China usually revolve around language, identity, and differences in political convictions.
What did the short story say?
The fictional essay at the centre of the political storm is titled "Our Time" and was submitted by an independent author to a 2020 writing competition hosted by Mr Chan's organisation and funded by the Hong Kong government.
It tells the story about a man who emigrated from Hong Kong to the UK with his parents in 2020 - the year the national security law was imposed. After the death of his parents in 2050, the man visits Hong Kong, only to find the city's history scrubbed away by authoritarian rule.
The article ends with a phrase, "The struggle of man against power is the struggle of memory against forgetting." It was written by the late Czech novelist Milan Kundera, whose many books usually contained themes around Czechoslovak Communism.
The officers wanted the short story on the association's website to be taken down, failing which, they said, Mr Chan could be wanted by the national security department.
'I cannot go back'
Mr Chan said he felt threatened after he contacted the Hong Kong authorities.
"In the conversation, I found that they pretty much have knowledge of where I worked and also the activities of the Hong Kong Language Learning Association," he said.
Hong Kong authorities have not addressed the matter directly. The BBC has reached out to the National Security Department for comment.
Mr Chan, whose family remains in Hong Kong, said he did not know where he could go now. "I am now travelling in Australia. I did not plan to stay. It was just a vacation. I still haven't figured out where I can settle as I cannot get back to my hometown," he said.
The closure of the Hong Kong Language Learning Association has revived some debates around whether Beijing is trying to replace Cantonese with Chinese.
"For the Hong Kong people, the rhythm and cadence of Cantonese is theirs. Losing Cantonese would mean losing a central part of their being, in some sense becoming immigrants in their own land, " said Norman Matloff, a professor at UC Davis who speaks both Chinese and Cantonese.
However, Mr Chan believes the reason his organisation got into trouble is because the essay in question was shortlisted in a writing competition with funding from the government.
"Supporting Cantonese had become an excuse for them to report us under the national security law," he said.