Background . The story of
Papa is based on the
2010 Heung Wo Street Murder. On 22 July 2010, a 15-year-old teenager Kan Ka-leung murdered his mother Lam Lin-kam and his younger sister Kan Chung-yue at home, before turning himself in to the police after wandering the streets for a short period. The family, which included the father Kan Fuk-kui, lived together on Heung Wo Street in
Tsuen Wan. After having a family dinner at their restaurant on the night of the murder, the mother and children returned home while Kan Fuk-kui stayed behind to run the restaurant, thus escaping the murder. His psychological assessment diagnosed him with
schizophrenia and revealed that he suffered from
auditory hallucinations during the murder, hearing voices told him to eliminate part of the population on a mission to solve the problem of
overpopulation, resources waste and harm to environment. Yung, who grew up in Tsuen Wan and lived nearby Heung Wo Street, was already familiar with the murder case before the film's production and cited his familiarity with the crime scene as essential for capturing the film's
sense of place. Yung felt that Kan initially was defensive and reluctant to have his story adapted, as he did not want the public to cast judgement on his son. Originally, Yung planned to adapt the murder into a
true crime film involving
mysticism, as he found newspaper articles that mentioned
occult symbols being found outside the Kans' apartment. For instance, the film included scenes of the father writing letters to his deceased wife, inspired by real advice from psychiatrist to Kan as a form of
narrative therapy. Yung stated that his motivation for creating the film was to raise awareness of families affected by
mental disorders and to demonstrate how to process emotions for
Hongkongers. Yung credited Au as co-director in recognition of his contributions to the film. Adopting a narrative style similar to that of
Port of Call and
Where the Wind Blows (2022), Yung used a
stream of consciousness and wrote the screenplay from the father's perspective, focusing on his navigation of the aftermath of the murder while the arcs of the other characters unfolded around him.
Mikio Naruse's
Mother (1952) was also cited as an influence on both the film's aesthetics and the subtle emotions translated through family members' interactions. but the project was subsequently
stalled in development when the director dropped out to work on a Hong Kong-Chinese film. Yung, still fond of the screenplay and feeling confident in his filmmaking skills after making
Port of Call, reached out to the director and had been in talks for seven to eight years to buy back his script. After Yung confirmed the film's production, he approached Koo for the role of the mother, before
Sean Lau was cast as the titular father. He cast Koo because he believed she embodied a charisma that was "both gentle and strong", similar to his own mother. noting the strong contrast in Lau's appearance and personality, which suited the character. However, Yung insisted on casting Lau and waited three years for his agreement, during which investors suggested changing the lead actor, but Yung refused. A culinary coach was hired for Lau, who did not know how to cook, to help him prepare for his role as a
cha chaan teng owner and learn to make
soy sauce chicken. Lau voluntarily lowered his salary due to the film's budget constraints. Yung held auditions and screened over a hundred actors but was unable to find a suitable candidate for the role of the son. After seeing So's photo, Yung felt that his demeanor matched his vision for the character and cast him in the role.
Yeung Wai-lun, the lead actor from
The Sparring Partner (2022) produced by Yung, returned to star in this film and offered advice to So on portraying a murderer. , who worked with Yung as the
acting coach for
The Sparring Partner, also reprised her position. Cameo appearances by ,
John Shum, and were featured, with Yung explaining that he cast these actors based on the characteristics that the audience was most familiar with, aiming to evoke a sense of nostalgia for past Hong Kong cinema. In June 2022, the film was
greenlit as part of the
Hong Kong Film Development Council's Operation Greenlight with a budget of
HK$7,246,400 through the Film Production Financing Scheme, with Sean Lau and Jo Koo announcing as the lead cast and producing. After producing
The Sparring Partner, Yung found himself in debt and had to make a low-budget Chinese romance film,
Penny Pinchers (2024), to repay it while on holiday that same year and postponed
Papa production. He returned to Hong Kong to direct
Papa right afterwards, a film he described as a real "Hong Kong film", in contrast to
Penny Pinchers, which he characterised as a "very mainland Chinese film". Yung teased the production of the project in the same month, describing it as a "small-scale
art-house film" and expressing uncertainty about
whether it could be released in China. Sean Lau and Jennifer Yu reportedly joined the production on 17 March, with filming continuing through April. Lau took a hiatus to attend the
41st Hong Kong Film Awards on 16 April before returning to shoot the following day. The shoot wrapped up within the first half of the year. Yung used a
4:3 aspect ratio during filming to create "the sensation of watching a
home video rather than a feature film", enhancing the film's casual atmosphere and making it feel like "a glimpse into everyday life in a typical household". All but one scene in the film used
eye-level camera angles, which Yung described as making the audience "feel as if they are standing next to or behind the characters" and allowed for a subjective interpretation of their lives, citing inspiration from
Huang Hsin-yao's
The Great Buddha+ (2017). Yung chose Mei King Street because his production company's office was nearby, and he felt the landscape and architectural style of the
tong laus there resembled those of Heung Wo Street. However, while on set, he found the atmosphere and the cast's emotional state deeply immersed in the situation, which led him to improvise the shoot.
Post-production , who collaborated with Yung on
The Sparring Partner, edited the film. They decided to use all five family members (including the house cat Carnation) as chapter titles, with each chapter centering on a specific family member while also connecting to the others. and was presented at the
Hong Kong Filmart in March 2024. On 25 September, the film's teaser poster was released along with the announcement of its world premiere date. In November, a member of the
Cantopop boy group
Mirror was reported to have a cameo appearance, and Philip Yung revealed that it was
Edan Lui in the same month. Lui's cameo scene was not included in the original screenplay and was added as a last-minute shoot, because Yung wanted to "add a touch of hope" at the end as he believed society was in greater need of it compared to the time when he was writing the screenplay. Yung met Lui while he was the lead in '''' (2026), another film Yung produced that year, and recognised his acting potential after watching him in three other films of various genres, inviting him to make a cameo.
Music The film was scored by Chinese musician Ding Ke, Yung chose the song for its sense of vintage, aiming to evoke the nostalgia of older Cantopop to resonate with the pasts of Sean Lau and Jo Koo's characters.
Fung Ka-ming of
Ming Pao noted that, much like
Port of Call used
Sammi Cheng's "
Aerial View of My Life" to weave through the narrative,
Papa song choice echoed and captured the film's theme of love; while Cyrus Lamprecht from the
Hong Kong Economic Times compared the film to
Ann Hui's
The Story of Woo Viet (1981), which also used the song as an
intermezzo, observing that both films share a similar message about the protagonists letting go of their obsessions and freeing themselves from their tragedies. == Themes ==