your older sister
Honorific pronoun used to refer to the addressee's older sister, mainly in formal letters.
Please give my regards to your older sister.
Used primarily by men in letters to address an older woman respectfully. Rare and old-fashioned.
I am always indebted to you (older woman).
Compound of 貴 (honorific prefix) and 姉 (older sister). The exact historical derivation is uncertain, but the spelling is conventionally associated with respectful address.