Kimi wo Wasureru 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 reunites with her ex-boyfriend, who somehow changed into a different person?! However, there's still this certain spark between them.

(From Lovesick Alley)