the FL's sister just married the ML's brother. But their siblings suddenly die from a car crash. The mc's get into a fight at the funeral and got into a car crash but they travel back in time when they were classmates, before their siblings met each other. the main characters try to prevent their siblings from meeting so they don't die. FL has her sister's diary to reference when the two meet. But it comes with consequences since the sister has a stalker making more problems. FL and ML also start getting close and clear up misunderstanding that happened in the past of the original timeline.
Goodbye, In-law