Kadua munroi is a compact shrub or small tree, growing between 1.5 and 2.5 meters tall, adapted to the harsh conditions of windswept ridges and upper slopes in wet forests. The leaves are simple and opposite, with oblong-elliptic to elliptic blades, occasionally showing elliptic–ovate or elliptic obovate shapes, measuring 3 to 10.5 cm in length and 2 to 5 cm in width. These leaves are firmly to moderately concave with an obtuse or rounded apex that ends in a short–cuspidate tip and a rounded to weakly subcordate base. They feature a coriaceous texture, glabrous upper surfaces, and lower surfaces that are moderate to sparsely short hirtellous, typically along the principal veins. The margins are entire and revolute. The lateral veins of the leaves are firm to moderately impressed and arcuate, with the higher-order venation ranging from relatively inconspicuous to conspicuous. The petioles are short, ranging from 0.1 to 0.6 cm, and the stipules are present, measuring 3–5 mm long and adnate to the petioles only at the base. The flowers are found in terminal, congested paniculate inflorescences measuring 1.3–5 cm long, with a hispidulous peduncle and secondary branches. Pedicels range from 0.8 to 3 mm in length and are usually glabrous. The flowers are bisexual and insect-pollinated, featuring a green corolla with a sometimes purple tube. The corolla is fleshy and salverform, measuring 4.3 to 11 mm long, with a weakly quadrangular limb and linear lobes, each ending in a fleshy appendage. The calyx is 4-5-lobed with deltate lobes. There are as many stamens as the corolla lobes, and they are inserted midway or near the throat of the corolla tube. The anthers are dithecal, opening by longitudinal slits. The ovary is inferior or partly so, 2(-4)-locular with few to numerous ovules on fleshy placentas. The style is cylindrical to filiform and terminal, with a bilobed or subcapitate stigma that is either included or exserted. The fruit is drupaceous, dark blue to purplish-black, and 4–7 mm in diameter, with persistently spreading calyx lobes. It is found in the Ko‘olau Mountains on O‘ahu and Lāna‘ihale on Lāna‘i between 610 – 1000 meters.