A lodging house specifically for geisha. The inhabitants may include: Okasan (Mother, owner, proprietress), Geiko, Maiko, Shikomi, and Maids and/or Cook. Contrary to popular belief, men (except priests and dressers) are not allowed inside the okiya. Sexual relations in an okiya is frowned upon and rare.
When the two maiko finished class, they returned home to the okiya.
In the world of geisha, the word onesan (pronounced oh-neh-sahn) means 'older sister'. Every maiko (apprentice geisha) has an onesan. When a maiko has her misedashi (formal debut) she goes through san san kudo. San san kudo is a binding ceremony, where a maiko and geiko (geisha) are legally bound as sisters. A maiko's onesan gives her advice and helps her in the complicated world of geisha. A maiko's onesan is always in the same hanamachi (geisha district).
Right now I am only a minarai, but when I have my misedashi, I will be formally bound with my onesan.