[3] Japonolirion osense is a herbaceous, perennial plant with subterranean creeping rootstocks.

Its green, linear leaves a set in a rosette, and are 3–20 cm (1.2–7.9 in) long and 1–4 mm (0.039–0.157 in) wide, with 7-9 veins, and rough margins.

The flower stalks emerge from shoots that carried leaves during the previous year, so it stands separately from the current leaf rosette.

There are 6 stamens of about 1.5 mm long, each carrying a yellow anther.

The ovary matures into three free green carpels that later develop into oval capsules of about 2.5 mm in length.