Mydas flies (Diptera, Mydidae) are primarily found in arid and semi-arid regions, with few records from East Asia. In Japan, Nemomydas gruenbergi (Hermann, 1914) is the only known species, previously reported mainly from southern Iriomote and Ishigaki Islands in the Yaeyama Islands, with very few records from northern Iriomote. Here, we report newly confirmed occurrences from northern Iriomote Island, based on direct observations and specimen collections conducted in summer. Observations include, for the first time to our knowledge, photographic documentation of a mating pair and confirmed oviposition behavior.