noun
biological older sister; real elder sister
Used to specify a blood-related older sister, as opposed to a sister-in-law (義姉) or stepsister. Common in formal writing, family registers, and when clarifying relationships.
彼女は私の実姉で、三つ年上です。
She is my biological older sister, three years older than me.
戸籍には実姉として記載されている。
She is listed as a biological older sister in the family register.