백사부인(1960) / Madame White Snake (Baeksabu-in)

A thousand-year-old snake takes the shape of a woman, marries a young pharmacist, and holds on to the marriage against a rival who wants her and a Buddhist order to return to the spirit world by the seventh day of the seventh month. Shin Sang-ok stages the White Snake legend with transformation scenes and folk-horror trappings before granting the couple a reprieve.

Why it's free: Free on the Korean Film Archive's own channel; KOFA holds the rights to the restorations it publishes.