Responses
I have one belief. If they end up together up until the end of the story and through the epilogue as well as possible sequels, that meant they loved each other for the rest of their life. It's a general rule of fiction, supported by fairy tales, and a happy way to end everything. Real life is full of insecurities, so why doubt the happy ending? They showed the latter part here, which meant that's how it ended. But for the rest, it should be okay to believe in a happier, sweeter ending.
The first story cracked my faith on the stories that i've read that have couples that got together in their school days.