Also: "onee-san (お姉さん)", "onee-sama (お姉さま)", "onee-chan (お姉ちゃん)", "nee-sama (姉さま)", "nee-san (姉さん)", "nee-chan (姉ちゃん)", "ane-ue (姉上)"

"Older sister"—like nii-san, one of those very simple terms which is unfortunately difficult to translate because of the differences in usage between English and Japanese. In Japanese, it is much more natural to call your (older) sister "nee-san" or "onee-san" rather than by their given name. It connotates a degree of respect and at the same time a certain closeness. ("Onee-sama" indicates more formality; "ane-ue" indicates even more formality, i.e. "honorable sister"; "onee-chan" indicates less familiarity.)

One can also use "onee-san" to refer politely to an unrelated slightly older female.

In Mirage of Blaze, Takaya initially calls Ayako "Onee-san" (actually, "おねーさん") and later "Nee-san" ("ねーさん"), which has a somewhat slangy feel to it, and might actually be translated as "Sis" if it had the same rough connotation as "Bro".