Stenogyne kauaulaensis is a scandent or decumbent vine growing several meters long. The stems are flexuous and spreading, measuring 1–2.5 m long, with a terete (cylindrical) or weakly 4-angled shape. They are evenly pubescent to moderately tomentose, with hairs spreading to slightly antrorse and occasionally glandular, often displaying a pink to purple-red tinge in young stems. The leaves are simple and opposite, with broadly ovate blades measuring 3.5–7(–9) cm in length and 2.5–4.7 cm in width. The apex is acute to attenuate, and the base is cordate, rarely truncate. Upper surfaces are glabrate with sparse pubescence along the midrib and veins; lower surfaces range from sparsely to densely pubescent, particularly along the midrib and veins. Blades are light green and membranaceous. Margins are broadly crenate, occasionally crenate-denticulate. Petioles are 7–18 mm long, densely pubescent, and show a pink to purple-red tinge in young growth. There are no stipules. The flowers occur as 5(6) per verticillaster (inflorescence that resembles a whorl but consists of two crowded cymes on either side of the stem), axillary, with 2(3) raised on 2–9 mm pubescent peduncles. Bracts are linear-filiform to subulate-filiform, often reflexed, measuring approximately 6 x 1 mm, and are pubescent. Pedicels are 7–11 mm and pubescent, occasionally glandular. The calyx is radially symmetrical, broadly campanulate, inflates in live material, and separates from the base and tube of the corolla, measuring 17–24 mm and enlarging in fruit. It is pubescent to glandular-pubescent, becoming glabrate in fruit, with lanceolate-deltate, foliaceous teeth measuring 7–10 x 5–8 mm at the base. The corolla is bilabiate, purple, and pubescent externally with scattered longer glandular hairs, glabrate within, and shows a light green tinge clouded along the inner throat. The tube is narrowly funnelform, strongly falcate, measuring 20–24 mm, with an upper lip entire or 2-lobed and a lower lip with three lobes. There are four purple stamens, exserted beyond the upper corolla lip. The fruits are black nutlets, ca. 8 mm long, 1-seeded, drupaceous, with slightly winged margins. The exocarp is fleshy, and the seeds lack an endosperm or are scanty and oily. It is found on steep to vertical rocky slopes and windward-facing ridges at 975–1,075 meters.