shiriaishiりあいriaishiriあいai
1.

A person with whom one has a mutual understanding, familiarity, or connection that is more than superficial, often established through social interactions.

2.

The state of being familiar with someone, characterized by a degree of knowledge about each other's backgrounds, interests, or situations, typically as a result of prior interactions.

3.

A relationship involving an individual one knows moderately well, but not to the extent of being close friends or intimate companions, often resulting from shared experiences or social circles.

Example:

どこで彼女と知り合いになったのか。