noun
Borrowed from English, used in the same figurative sense as in English: the hidden, negative, or evil aspect of something or someone. Often appears in contexts like Star Wars or discussions of personality.
彼にはダークサイドがある。
He has a dark side.
フォースのダークサイドに堕ちる。
Fall to the dark side of the Force.
Variant with interpunct, sometimes used for clarity or stylistic effect.
Direct loan from English 'dark side', adopted into Japanese with the same meaning.