"Koshino-kan-aoi" (Heterotropa megacalyx) belongs to Aristolochiaceae (the Birthwort family). It is an evergreen herb that is distributed to the Japan Sea Side of Honshu, from the southern part of Akita Prefecture to the northern part of Nagano Prefecture. This herb grows in deciduous broad-leaved forests, from lowlands to mountains, up to a height of 10-20 cm. The rhizomes are dark purple and thick, and they scrawl the ground. The leaves are ovate-broad-elliptic or ovate-hastate, with acute tips, cordate bases, and long petioles. The surface of the leaf is dark green, has no gloss, mottles or no mottles. The dark purple or light purple flower will bloom at the tip of the stem from March to May. The flowers have not petals, on instead petal-like calyx lobes. It is a foodplant for Gifu butterfly (Luehdorfia japonica) caterpillars.