Translation guide
In Japanese, there is no single common word for 'stepsister'. The way you refer to or describe a stepsister depends on the family relationship, formality, and whether you are speaking about your own family or someone else's.
When talking to or about your own stepsister in a casual, everyday context.
In Japanese families, siblings are usually addressed by name, not by a kinship term. This applies to stepsiblings as well. Use the appropriate honorific based on age and closeness.
花子ちゃん、一緒に遊ぼう。
Hanako, let's play together.
Literally 'sister-in-law (younger)'. Can be used to describe a younger stepsister, but it is more common for in-laws. In a stepfamily context, it may sound a bit formal or explanatory.
彼女は私の義理の妹です。
She is my stepsister (younger).
Literally 'sister-in-law (older)'. Used for an older stepsister, but again more typical for in-law relationships.
義理の姉は大学生です。
My stepsister (older) is a college student.
When you need to clarify the family relationship to someone outside the family.
This phrase means 'child from a parent's remarriage partner'. It is a clear, neutral way to explain the step-relationship without using a specific kinship term.
彼女は父の再婚相手の連れ子で、私の義理の妹になります。
She is my father's remarriage partner's child, so she is my stepsister.
A general term for 'step-siblings' or 'siblings-in-law'. You can specify gender and age if needed.
義理の兄弟姉妹が二人います。
I have two stepsiblings.
When speaking politely about another person's stepsister.
Polite way to refer to someone's older stepsister. Use お姉さん for older, 妹さん for younger.
田中さんの義理のお姉さんは医者だそうです。
I heard that Tanaka's stepsister (older) is a doctor.
Polite way to refer to someone's younger stepsister.
義理の妹さんはおいくつですか。
How old is your stepsister (younger)?
There is no exact equivalent of 'stepsister' in Japanese. Using 義理の姉/妹 can be ambiguous because it also means 'sister-in-law'. In casual contexts, it's more natural to use names or explain the relationship.
In Japanese family culture, siblings (including step-siblings) typically call each other by name with appropriate honorifics, not by kinship terms. This is the most natural way to address or refer to your stepsister within the family.