According to Official Guinness Records,
The most consecutive Japanese No. 1 singles since debut is 39, achieved by KinKi Kids (Japan), between 28 July 1997 and 5 February 2018.KinKi Kids is a popular Japanese duo comprised of two singers, Koichi and Tsuyoshi Domoto. Their 39th No. 1 single is titled 'Topaz Love / DESTINY'.
For a complete list of 2018 records, please visit 2018 Guinness Records in Japan.