If you describe someone, usually a young woman, as demure, you mean they are quiet and rather shy, usually in a way that you like and find appealing, and behave very correctly.
She's very demure and sweet...
The luscious Miss Wharton gave me a demure but knowing smile.
Demure clothes do not reveal your body and they give the impression that you are shy and behave correctly.
...a demure high-necked white blouse.
There is relatively little information about demure, maybe you can watch a bilingual story to relax your mood, I wish you a happy day!