I thought of something but it is quite somber, so be warned if you are not up to it.
This is not something that I per se would have to confess but it is somewhere up there. In high school one of the girls in my class was to get married righter after graduation. I didn't know her future husband and had never met him, but I knew her and she even invited me to her wedding, which I could not attend. Before graduation we had something like a class trip somewhere. On that trip however, she made out with said friend which I personally find quite terrible. After the trip she even invited him to the wedding, which I never understood why exactly. Sufficed to say he didn't attend it, and neither did I, for a different reason though. I always wondered if I should have tried to get in touch with her future husband. As far as I know they got married soon after, but I don't know what happened afterwards. Don't know if this is a confession per se though.
@SanguineTear what's wrong with Sylveon, it's great!