Konna Mirai wa Kiite Nai!!

Kayo Hanazono, a second-year high school student, has been hiding her feelings for her childhood friend Shinnosuke, and she thought she'd be safe doing so. But then Kayo's 30-year-old self appears from the future! She is told that Shinnosuke is getting married to another girl he has been dating since high school, and that Kayo is still single at 30...