Aw man, this is so sad, norino actually decided to make a prequel set 10 years prior to show Misaki's tragedy in full, back when she was 18 years old and her sister Manami was just 10. The events in which Manami was dating her boyfriend Tomoki and hoped they would marry and be together forever, Misaki's parents were even ok with it, they approved Tomoki as their son-in-law, and little Manami liked Yuki as her big bro too!
Still, tragedy came knocking, one day Misaki's parents car broke in the middle of traffic, they called home to calm Misaki down but Misaki offered to go there with Tomoki to pick them up, but this prequel adds the detail that Tomoki ended up being an accidental angel for Misaki, he told her he would go alone, it's better for Misaki to stay home, focus on her upcoming exams and watch over little Manami, the original series had Misaki blame herself for being the one who asked Tomoki to go, when here she volunteered both of them but Tomoki decided to go alone, and little Minami wanted to go with him to play won't her big bro but Misaki tells her sister she would get in the way, it's not time to play, but Tomoki swears he will play with Manami once he gets back!
But as it was always known they never came back, Tomoki and Misaki's parents died in a car crash, she is utterly horrified by the news and later her uncle confirming it, asking Misaki to please be strong and come recognize the bodies; Misaki loses her mind in despair, blaming herself for causing this, she should die too! NO! Once Misaki sees her little sister Manami she goes to take care of her in her parents' place, yes, she takes over her family's business, places her engagement ring with Tomoki in her resolution box, swearing any romance off as she focused on leading her family's company and raising Manami for the foreseeable future, THE END. -----------
Well tragedy aside everything will get better and happy 10 years from now on, Manami will meet Tomoya who's a carbon copy of Tomoki, and she shares him with Misaki, nice!
norino is business sawvy and directs the reader to buy the original series right away to get that happy ending after this sad ending, and says he is working on a new mom and daughter series too, cool.