Mikazuki to Nagareboshi

From Whitelies Fansub: Hasegawa Mitsuki, a college freshman. Mitsuki has been thinking about the same person since she was 16 years old. That person, being 18 years older. A Coffee Shop Manager, Asai Ryusei, a widower with an only son. To Mitsuki, Ryusei is a really important person but, her romantic interest for him is slowly...?!