Okuremashite Seishun

Wakaba Kayano is a 20-year-old college student who was too busy studying in high school to experience the quintessential personal milestones of her teenage years, like going on an afterschool date. In a moment of desperation, she goes out on Halloween in her old high school uniform in an effort to take back some of those heart-fluttering experiences she never had, and in doing encounters Fumito, a boy clad in the quintessential high school boy uniform. Whisked away on the date of her dreams, she panics when forced to reveal her true age—only to find out that Fumito is in college, too!

(Source: Kodansha USA)