Mai's research focuses on public attitudes to the death penalty. She used survey work, social experiments, and deliberative consultation as her methodology to determine the effect of information and deliberation on support for the death penalty. Her monograph 'The Death Penalty in Japan: Will the Public Tolerate Abolition?' (Springer, 2014) received the Young Criminologist Award 2014 from the Japanese Association of Sociological Criminology.
In August 2015, she completed a 2-year project funded by the UK, German, Swiss and Norwegian foreign offices, the European Commission, and the Daiwa Foundation (£150,000). This involved further empirical work on the death penalty in Japan. The final report 'The Public Opinion Myth: Why Japan Retains the Death Penalty' is available in English and Japanese. She is also engaged in consultancy work for international organisations (UN) and has collaborated with the Death Penalty Project, a London-based NGO.
She was awarded the Embark Award in July 2017 for her work on the death penalty.