Kimi o Wasurareru Koi ga Shitai
Once a delicate teenage romance between a boy and a girl, who shared all of their firsts. But then they broke up and the boy moved to Tokyo. Years later, the girl goes to college in Tokyo where she meets her ex-boyfriend again, who somehow changed into a cocky womanizer?! But there's still this certain spark between them.
(Source: Manga Mogura RE, edited)