with Koo in 2010 After 1989, Koo became committed to Hong Kong's social movements, showing up in different protests, including
1 July marches, and continued after the
handover of Hong Kong in 1997. Koo was always seen protesting with
Leung Kwok-hung, an ex-MP known as "Long Hair" (長毛) who was also a left-wing activist, and best known for carrying a handmade coffin to protests to show his disapproval of Beijing. As part of the
Baodiao movement, he landed on the
Senkaku Islands, or Diaoyutai Islands, on 15 August 2012. He and others were arrested by Japan, and released two days later after Beijing's intervention. At a televised press conference after arriving back in Hong Kong, Koo swore at a man behind him, telling him to "move over,
diu nei lou mou ('fuck your mother!')" (), which surprised audiences and became a local
meme. Following the imposition of the
national security law in 2020, Koo said he disagreed with violent clashes and the
Hong Kong independence movement, but admitted only radical acts could be effective as both the PRC and Hong Kong Governments no longer tolerate peaceful protests. Koo also called on youngsters not to give up even if jailed for marches and assemblies, saying the authorities should take the blame.
Convictions and jail with the famous mock coffin in 2013 Koo was jailed at least twelve times over different offences. In 1998, Koo, along with
Tsang Kin-shing,
Leung Kwok-hung, and Lau Shan-ching, was fined HK$3,000 for disorder in public spaces over burning mock coffins during the visit by
Jiang Zemin,
paramount leader of China. In 2000, Koo was jailed 14 days over two protests during Legislative Council proceedings. In 2001, Koo was fined
HK$3,000 for graffiti on a
Hong Kong emblem during a protest. Between 2012 and 2018, Koo was jailed for his multiple burnings and desecrating of the
PRC and
Hong Kong flags. The jail term was reduced to 4.5 months on appeal. he celebrated his fifth jail sentence near the court. On 27 March 2018, Koo was jailed for the sixth time, after desecrating the PRC and Hong Kong flags during a candlelight vigil in memory of
Nobel Peace Prize winner Liu Xiaobo in 2017, and during the Chinese National Day protest in 2017, and the New Year march in 2018. He was sent to jail for six months before chanting "all hail democracy", "all hail human rights", and "say no to the Chinese Community Party". On 25 June 2019, Koo was jailed for six weeks after desecrating the Hong Kong flag by writing "Shameful Hong Kong Government" in protest against disqualifying
Lau Siu-lai's MP seat, amounting to his seventh jail sentence. On 28 January 2021, Koo received his tenth jail sentence of four months after desecrating the PRC flag by writing "white terror" and "fascist horror" and flying it upside down, to voice out support with 15 democrats charged with illegal assembly. He vowed in court to breach the
National Security Law imposed upon Hong Kong by the PRC. On 14 April 2021, just days after finishing his earlier jail term, Koo was jailed for five months over illegal assemblies with
Joshua Wong on 5 October 2019, the day the
Prohibition on Face Covering Regulation was enacted. Koo was again arrested on 4 February 2022, reportedly under the security law for suspected incitement of subversion, before his planned demonstration outside the Hong Kong Liaison Office to protest the
PRC's Winter Olympics and call attention to political activists behind bars. Koo was charged with attempting to commit a seditious act over a one-metre long coffin and a white flag with language including "down with the Chinese Communist Party" and "end one-party rule" found at his home, and was denied bail. He was jailed for 9 months after the judge found him guilty. On 18 December 2023, Koo was fined HK$6,000 for breaching fire safety regulations. The
Hong Kong Fire Services Department had not informed him of their removal of his belongings from the open areas in an industrial building. Local media reported that he had been in hospital at the time of the removal. On 16 February 2024, Koo was sentenced to nine months in prison for "attempting or preparing to do an act with a seditious intention", after he was found guilty of planning a protest against the
2023 District Council elections. He was released in September 2024. == Personal life and death ==