"In the study of history as an academic disciplinary, a primary source (also called an original source) is an artifact, document, diary, manuscript, autobiography, recording, or any other source of information that was created at the time under study." (Wikipedia)
Here are a few library databases containing primary source material that may support research on topics related to East Asia. For more primary source databases, see the History Research Guide, which organizes primary sources by region, time period, and source type.