After the female protagonist caused the male protagonist's family to be destroyed, the male protagonist lost his memory. Five years later, the female protagonist returned and the male protagonist fell in love with the female protagonist again. He was stabbed at the wedding and recovered his memory to imprison the female protagonist.

This plot seems to be one of the common plots in online novels. Here's my answer: After the female protagonist caused the male protagonist's family to be destroyed, the male protagonist lost his memory and the two lost contact. Five years later, the female protagonist returned and the male protagonist fell in love with the female protagonist again. However, the female protagonist did not know this history and the two began a new relationship. However, at the wedding, the male protagonist was stabbed and regained his memory. He realized what he had done and decided to imprison the female protagonist to prevent her from returning to the past. This plot is often used to express the protagonist's guilt and remorse, as well as the impact of their inability to forget what happened in the past.