Tokyo is a top donor to Myanmar and has long-standing relations with the country’s military.
In September, Japan’s defence ministry it will halt a training programme for members of Myanmar’s military from next year over the junta’s executions of pro-democracy activists.
Since 2015, Japan has received 30 members of the Myanmar military as students at facilities including the National Defence Academy.
The programme is intended to help the students acquire “correct knowledge about democracy and civilian leadership” of the military, through interaction with Japan’s Self-Defence Forces, the defence minister told parliament in April.
The already isolated junta stoked further international outrage in July when it announced the execution of four prisoners, in the country’s first use of capital punishment in decades.
Myanmar’s junta has clamped down on press freedoms, arresting reporters and photographers, as well as revoking broadcasting licences.
Kubota is the fifth foreign journalist to be detained in Myanmar after US citizens Nathan Maung and Danny Fenster, Robert Bociaga of Poland and Yuki Kitazumi of Japan – all of whom were later freed and deported.
Fenster, who was held in May last year as he attempted to leave the country, faced a closed-door trial inside Insein on charges of unlawful association, incitement against the military and breaching visa rules.
He was sentenced to 11 years in prison before being pardoned and deported.