Micropterigidae is considered to be the sister group of all other extant Lepidoptera. In Japan, 17 species of five genera have been recorded including three endemic genera,IssikiomartyriaHashimoto, 2006,KurokopteryxHashimoto, 2006 andNeomicropteryxIssiki, 1931, all of which are associated with the liverwort genusConocephalumHill. We discovered four new species ofIssikiomartyriafrom snowy regions in Northeastern Japan, and two new species of a new genusMelinopteryxgen. n.from the subalpine zone of the Akaishi Mountain Range. All these new taxa,I.hyperboreasp. n.,I.leptobelossp. n.,I.catapastasp. n.,I.trochossp. n.,M.coruscanssp. n.andM.bilobatasp. n.are also associated withConocephalumliverworts. Furthermore, females ofI.akemiaeHashimoto, 2006 andI.plicataHashimoto, 2006 are described here for the first time. Our extensive surveys revealed that the fine-scale endemism ofIssikiomartyriarestricted to the fragmented area facing the Japan Sea. Keys toIssikiomartyriaspecies based on the adult morphology are provided.