The thing that Liang Rui regrets most in his life is that he didn't win that person's heart and could only watch that person being used and betrayed. No matter how he tried to persuade him, it would only push him further.
In the end, Liang Rui died to save him. After his death, Liang Rui actually returned to his junior high school days, before he met that woman.
A beautiful monster seduces a loyal dog into a pseudo-abstinence attack