also: ゆめおち
noun
it was all a dream ending
A narrative device where the story concludes by revealing that the preceding events were only a dream. Common in manga, anime, and light novels.
あの映画のラストは夢オチだった。
The ending of that movie was an 'it was all a dream' twist.
夢オチは読者にがっかりされることが多い。
An 'it was all a dream' ending often disappoints readers.
どんでん返し is a general plot twist, while 夢オチ specifically refers to the 'it was all a dream' revelation.
Compound of 夢 (yume, 'dream') and オチ (ochi, 'punchline' or 'ending'), from the storytelling term 落ち (ochi).