abrupt plot twist; unexpected story development
Colloquial term, often used in anime/manga/game fandom to describe a sudden, extreme, or nonsensical turn in the story that feels like it came out of nowhere.
In the final episode, aliens suddenly appeared—what an abrupt plot twist.
That anime has an unexpected story development every episode; you can't predict what will happen next.
Compound of 超 (chō, 'super, ultra') and 展開 (tenkai, 'development, unfolding'). The prefix 超 intensifies the sense of an extreme or excessive plot development.