とうにん当人tounin
1.

The individual directly involved in a specific matter or situation, often implying personal responsibility or connection.

2.

The person in question, typically signifying the actual individual rather than a representative or someone else.

3.

The specific person being discussed or referenced, highlighting their role or perspective in a given context.

Example:

当人のいないところで悪口を言うべきでない。