HolorusiaLoew, 1863 (Diptera: Tipulidae) is a relatively large crane fly genus with a wide distribution in the Afrotropic, Australasian–Oceanian, Eastern Palearctic, Oriental and Nearctic Regions. Although the genus is well known to include the largest crane fly species, the immature stages are, thus far, only described for the larva and pupa of the North AmericanHolorusia hespereaArnaud & Byers, 1990.In this study, we describe for the first time the egg, larva and pupae of the JapaneseHolorusia mikado(Westwood, 1876). Larvae were collected from semi-aquatic habitats, from slow flowing areas of streams and small waterfalls where leaf litter accumulates; the larvae are detritivores and feed on wet, decomposing leaves. The larvae were reared to adults in the laboratory. Morphological characters of immature stages discussed with comparison with the North AmericanH. hespera. Male and female genitalia are illustrated and described in detail for the first time.