Katsushika Oi

Katsushika Oi was the third daughter of the ukiyo-e artist Katsushika Hokusai. Her name was Ei, and "Oi" is her art name. She married another artist but was divorced, and after returning home she assisted Hokusai's work. Her dates of birth and death are unknown; one theory holds that she was supported by the Maeda family of Kaga in the Ansei era and died in Kanazawa, while another suggests she may have lived into the Keio era.

She excelled especially at paintings of beautiful women, and Hokusai is said to have remarked that he could not match Oi at them. She is known for hand-painted works distinguished by exaggerated chiaroscuro and minute detail; works firmly accepted as hers are few, and only a dozen or so survive.

She is thought to have lived with Hokusai for nearly twenty years in his last years, and some opinions hold that hand-painted works under Hokusai's name include her substitute work or collaborations. The Menard Art Museum's Beauty Under Night Cherry Blossoms has no signature, but it is generally accepted, on grounds of style, to be by Oi.