The DESTA database lists 3 trade agreements that include both countries, the most recent being Comprehensive and Progressive Agreement for Transpacific Partnership (CPTPP) UK accession (2023).
Benefits
BothComprehensive and Progressive Agreement for Transpacific Partnership (CPTPP) UK accession, signed 2023.
BothJapan UK, signed 2020 and in force since 2021.
BothEC Japan, signed 2018 and in force since 2019.