Tokyo (AsiaNews) – “How are you doing? Do you want to see the factory?” a prison officer asked a Chilean inmate in Japanese at Fuchu Prison in Tokyo, in late October.
To communicate, they used a small translation device powered by artificial intelligence (AI) software. This allowed the Chilean man, who, upon his arrival at the facility, had been unable to understand instructions from the staff, to express his interest in working in the prison’s workshop.
The device, which fits in the palm of a hand, translates the words of both officers and inmates in a matter of seconds, transforming how communication takes place in Japanese prisons and detention centres that house foreign nationals.
Japan’s Ministry of Justice distributed approximately 200 of these units in the summer of 2025.
At Fuchu, where, as of the end of last year, more than 20 per cent of the 1,760 inmates (including both convicted prisoners and those held under other forms of detention) were foreign nationals without permanent residency, the device has helped overcome challenges that were previously managed through gestures alone.
Inmates are now also able to ask questions about prison rules: for instance, why it is forbidden to share leftover food, or why standing up is prohibited while working.
“It’s easier to understand their feelings when we can communicate with words. For rehabilitation and recidivism prevention, it’s important to appeal to their feelings rather than force them to obey,” said an officer tasked with outlining the rules to new arrivals.
Another staff member at Fuchu described the shift in how they interact with inmates: “Slowly but surely, we’re building a relationship of trust,” he said.
A system without interpreters
In Japan, individuals who do not speak Japanese are assigned to one of six facilities, including the Fuchu and Osaka prisons and the Tokyo Detention House, where interpreters are available.
However, there are only 28 such interpreters, so that the day-to-day management of these detainees, including during nighttime hours and holidays, continues to fall on prison staff.
To address this issue, the government has introduced AI-based translation tools in 129 of the country’s 171 detention facilities. These devices support approximately 90 languages and can also translate written text.
One criterium for selecting the service provider was a guarantee that the content of conversations would not be used to train the artificial intelligence systems.
Language as a tool for reintegration
According to data from the Ministry of Justice, as of the end of 2025, 2,779 foreign nationals were in custody, either serving a sentence, held in pretrial detention, or detained in lieu of paying a fine, up by 30 per cent compared to 2015.
Foreign detainees in Japan come from more than 20 countries; the largest group is from Vietnam (682 individuals), followed by China (510).
The language barrier also significantly hinders access to training and rehabilitation programmes.
Detainees who do not speak Japanese are rarely able to participate in rehabilitation courses, which encourage them to consider the victims' perspectives, or in vocational training programmes that offer qualifications and certifications useful for their eventual reintegration into society.
For Prof Tatsuya Ota, an expert in criminal policy at Keio University, it is necessary “to implement support for foreign inmates’ reintegration into Japanese society and recidivism prevention has grown, as there are cases in which they remain in Japan after release by receiving special permission to stay”.
